Uhmmm...
C/K 1/2t trucks got the RPO-MG5. (wide ratio)
S/10's got the RPO-M50. (close ratio
Thanks, my notes (in post #3) were in error in a big way. Now I'm sorry I started down this rabbit hole
You made me look deeper and it's more complex than I (and perhaps you) stated.
The spec sheet from the
1998 FSM I posted (see my post #3) indicates...
- the MG5 (NV3500 wide ratio) was used all 4.3L and almost all 5.0L, on both 1500 and 2500 models (only the 5.0L C/K 2500 2D excab), with exception where the 5.0L got the MW3 (C/K 2500 2D regcab MW3 NV4500)
- M50 (NV3500 close ratio) was optional (never std), and only on certain 1500 and 2500 vehicles
It appears the NW3 (NV4500) was used on all 5.7L and 7.4L for which the engine was standard equipment; there's a few cases there the 5.7L engine was "optional" and only a NV3500 is shown.
This isn't a "summary" above, the combinations seem quite engine and vehicle specific... which I likely makes sense.
Again, this is for 1998, I didn't check other years.
I'm not trying to make this ^^^ the definitive list of vehicle / engine / trans combinations.
@sewlow made me look more closely and I've learned, and am trying to show, that it's a widely-varying arrangement.