You're asking a lot of this old fart. That was a year ago. As I read it today they are presented as a range of sizes and not any one specific size except those first three named brands with part numbers and those sizes came from those listing. Actually if you go to the:
M38 TM 9-8012 under cooling system they are much more detailed in their assessment of the size stating width-3/8" and outside circumference 45 7/8".
The M38 earlier TM 9-804 lists width as 3/8", gives no length but shows angle 40 Degs.
The M38A1 TM 9-8014 only lists the width at 3/8".
The very early M38A1 TM 9-804A lists width 3/8" and angle 38 Degs and calls it a vee-wedge cogged belt.
M38's 51 ORD 9 Ord# 7697614 WO# 801699
M38's 55 ORD 9 Ord# 7697614 and show an optional WO# 806764
M38's 56 ORD 7 Ord# 590897 7/16" top width x 38 Deg's x 45 5/8" outside circumference.
M38's 56 ORD 8 Ord# 590897 Same measurements and also list a 3 belt set Ord# 8699837 which would go on the 100 amp alternator kit.
M38A1 56 ORD 9 Ord# 7697614, Day Rubber # S5203, WO# 801699 and as optional it lists Firestone # NDD153 with WO# 806764.
M38A1's 52 ORD 7 Ord# 590897 as a belt set of 2.
M38A1's 1959 TM 9-2320-208-20P lists only the alternator 3 belt set Ord# 8699837.
M38A1's 1966 TM 9-2320-208-20P lists Ord# 590897, FSN 3030-505-5893 2 belt set 7/16" top width x 38 Deg's x 45 5/8" outside circumference. and the alternator 3 belt set Ord# 8699837.
Hows that for a little variation in numbers!
