How can I easily identify M/J2/J3, Cubans add on whats available or "invent" solutions. Why do recommend an "M"?
Hello Marty,
Willys & Jeep Identification
Edited and corrected from Midwest Jeep Willys web site.

• Willys MB & Ford GPW 1941-1945 – .Windshield height 23", flat fenders, split windshield, no tailgate, recessed headlights top mounted windshield wipers, rear mounted spare tire, hood height 6". 5x5.5" rim bolt pattern. 80" Wheelbase. The Willys chassis front cross-member is tubular, while the Ford GPW is an inverted U shape. Axle ration 4.88:1. Body/chassis serial is on plate on dash and plate on left front frame rail.

Willys Jeep CJ2A 1945-1949 – Wheelbase 80”. Windshield height 25", flat fenders, split windshield, has tailgate, top mounted windshield wipers, side mounted spare tire, hood height 6". 5x5.5" rim bolt. Axle ratios 5.38:1.

Willys Jeepster VJ 1948-1951 - 2wd convertable sports car Jeep produced by Willys Overland on the 4-63 chassis (Willys 4x2 wagon).
Willys Jeep CJ3A 1949-1953 – Windshield height 27", flat fenders, one piece windshield, vent in middle of windshield, bottom mounted windshield wipers, hood height 6". 5x5.5" rim bolt pattern. 80" Wheelbase. Axle ratios 5.38:1. Top front of each wheel house angled back further so front seats have greater rearward tilt for more room behind the steering wheel. Handbrake in center of dash.

• Willys Jeep Truck 1947–1964 - Similar to the Willys Jeep Wagon, Wheel base is 118", Engines L4-134 Go-Devil, F4-134 Hurricane, 6-226 Super Hurricane I6, 1950-64 V-Shaped Front Grille.

• Willys Station Wagon 1946–1964 - Flat Grille 1945-49, Wheel base is 104.5", Engines L4-134 Go-Devil, F4-134 Hurricane, F6 6-161 Hurricane I6, 6-226 Super Hurricane I6, 1950-64 V-Shaped Front Grille.
• Willys Jeep M38 1950-1952 – Wheelbase 80”. Windshield height 27", flat fenders, one piece windshield, vent in middle of windshield, bottom mounted windshield wipers, hood height 6". 5x5.5" rim bolt, originally 24 Volt Ignition System. Axle ratios 5.38:1. Instruments mounted in center of dash on a removable plate. Hand brake left side of dash.
• Willys Jeep M38A1 1952-1966 - 81" Wheelbase, Windshield width 59", rounded fenders, two piece windshield, F4-134 Hurricane Engine, 5x5.5" rim bolt pattern, no Tail Gate, originally 24 Volt Ignition System. Axle ratios 5.38:1. Instruments mounted in center of dash on a removable plate. Left side glove box. Handbrake between front seats.
Willys Jeep CJ3B 1953-1964 - (M606 based on this jeep)Windshield height 22-1/2", hood height 10-1/2", one-piece windshield, has tailgate, bottom mounted windshield wipers, side mounted tire carrier. 5x5.5" rim bolt.

Dispatch Jeep DJ3A 1956-1964 - The DJ3A was a flat fender postal & delivery Jeep similar to the CJ3A except it was two wheel drive. The engine was the L4-134 "Go Devil" Flathead. All DJ models were 2wd. It was produced from 1956 until 1964

Jeep CJ5 1955-1975 - 81" Wheelbase and CJ5 with 81" wheelbase. Windshield width 59", round fender Jeep, one piece windshield, no factory door hinges, windshield retainer welded on vehicle, windshield at 90° angle to hood. 5"x5.5" rim bolt pattern.

Jeep CJ6 1955-1975 - ( M170 was based on this jeep) Wheelbase 101". Windshield width 59", round fender Jeep, one piece windshield, no factory door hinges, windshield retainer welded on vehicle, windshield at 90° angle to hood. CJ6 is the same basic vehicle as an early model CJ5 except with an extended rear body tub and 101" wheelbase for '55-'71 and 103" wheelbase for '72-'75. 5x5.5" rim bolt pattern.

Forward Control FC-150 1957-1964 - Wheel base 81", F4-134 Hurricane Engine, FC-150 models used the frame of the CJ-5, 78" bed.

Dispatch Jeep DJ5 1965-1982 - The DJ-5 was introduced in 1965. The DJ is the Postal Jeep most people recognize today. They also produced a long version from 1965 until 1968, the DJ-6. The DJ-5 was made by Jeep into the early 70's and production continued under AM General till 1982. All DJ models were 2wd.

Jeepster Commando C101 1967-1971 - Jeep roadster with either a full soft top, a half hardtop forming a truck. Wheel base is 101" forming the model number.
Jeep Commando C104 1972-1973 - Jeep roadster with either a full soft top, a half hardtop forming a truck. Wheel base is 104" forming the model number. Front Grille was changed from the traditional Jeep style design.
Jeep CJ5 1976-1983 - Windshield width 55", round fender Jeep, one piece windshield, factory roll bar, bottom mounted windshield wipers, factory mounted door hinges, windshield retainer screws on, sloped windshield. Measures 71-1/2" from door hinge to rear of vehicle. 5x5.5" rim bolt pattern. 83.5" wheelbase.
Jeep CJ7 1976-1986 - Windshield width 55", round fender Jeep, one piece windshield, factory roll bar, bottom mounted windshield wipers, factory mounted door hinges, has either no windshield retainer or screw-in design. Measures 81" from door hinge to rear of vehicle. 93.5" wheelbase. 5x5.5" rim bolt pattern.

Jeep CJ8 Scrambler 1981-1985 - Windshield width 55", round fender Jeep, one piece windshield, factory roll bar, bottom mounted windshield wipers, factory mounted door hinges, 103.5" wheelbase. 5x5.5" rim bolt pattern.

Jeep Wrangler YJ 1987-1995 - Windshield width 55", round fender Jeep, one-piece windshield, factory roll bar with horizontal supports, rectangular headlights and turn signal lights, and a squared off front grille. Comes with either half or full hard doors. 93.4" wheelbase. 5x4.5" rim bolt pattern.

Jeep Wrangler TJ 1997-2006 - Windshield width 55". Round headlights. Center Tailgate mounted spare tire carrier with brake light. Tailgate opens to the side. 93.4" wheelbase. Coil spring 5 link suspension. Equipped with both driver and passenger side air bags. 5"x4.5" rim bolt pattern.
Jeep Wrangler JK 2007-Present - Brand new design of the old Wrangler, new 3.8L V6 engine. Plastic front fenders and grill. Coil Spring 5 link suspension. 95.4" wheel base. 5 on 5" rim bolt pattern. Three Piece Modular hardtop. 2 door and 4 door versions.

Jeep Cherokee XJ 1984-2001 - First uni-body Jeep vehicle. Suspension is mounted to the sub-frame of vehicle. Coil spring front suspension with leaf springs in the rear. Available in both 2 door and 4 door versions, both versions have the same wheel base.

Jeep Grand Cherokee ZJ 1993-1998 - Larger than the XJ Cherokee, optionally V8 engine. The first Jeep vehicle to use the Quadra-Coil design. Optional Quadra-trac II transfer four-wheel drive system.
Jeep Grand Cherokee WJ 1999-2004 - Replacement for the ZJ with modern lines, larger interior space by putting the spare tire under the cargo area floor.
I did some editing of this page to increase accuracy.
The only advantage to you of the m series jeeps would be the heavier frames and springs.
Personally for what you describe I would use a CJ5 or CJ6 and in lieu of them I would consider the M38A1 or M170 (military CJ6). For the best ride and utility you cannot beat the CJ6.