Bill,
Some of the late model single coil per cylinder cars have coils that will fit in the M series distributors. One of our members has already done this and has a photo album full of the switch over photos. There are also 12 volt coils made that are the same dimensions as the original 24 volt units. These are out of production but still pop up for sale now and then.
As for ID'g plug wires many will interchange or work but original factory installations differed significantly between the M37, M38, M38A1/M170, and the M151.
M38:
7528173 Cyl # 1 23 3/4" long.
7528174 Cyl's # 2, 3, & 4 19 3/4" long.
Both ends are 90 deg elbows.
M38A1/M170:
8328449 4 Ea. 29" long.
Both ends straight.
M37:
Early engines up to eng sn 25519:
7528172 - 6 Ea. 24"
Eng sn's 25519 & up:
8328040 - 5 Ea. 24"
8328039 (superceded by 8741873) - 1 Ea. #1 cyl 22"
All three above are 90 deg. elbow one end and straight the other end.
M151 Series:
11660569-1 2 Ea. #3 & 4 cyl's.
11660569-2 1 Ea. #2 cyl.
11660569-3 1 Ea. #1 cyl.
As you can see below these are very short running 11" to 16".
M715:
11641027-1 Cyl # 1 18.5"
11641027-2 Cyl # 2 20"
11641027-3 Cyl # 3 22"
11641027-4 Cyl # 4 24"
11641027-5 Cyl # 5 29"
11641027-6 Cyl # 6 31.5"
All cable ends are straight.
