Kevin,
On the first one ...
Regarding the 1st trans, is there a gap between the '12' and the 7411612?
If so, it has a factory ZF limited slip differential.
The serial number is only supposed to have seven digits, and:
7 = 6 cyl. engine
4 = 5-speed, USA/Japan
1 = 1981
1612 = sequntial serial number
915/63 is the type number ... meaning the gearsets were:
8:31 ring & pinion
11:35 1st gear
18:32 2nd gear
23:29 3rd gear
26:26 4th gear
28:23 5th gear
2nd trans is '77 model 5-speed 915/61 with:
8:31 ring & pinion
11:35 1st gear
18:33 2nd gear
23:29 3rd gear
26:26 4th gear
28:23 5th gear