SM420 has a 7:1 granny gear.. tough and as short as it is makes it one of the best jeep trannies
The novak adapters site also has a "how to" on mating a ford transmission to a GM car bellhousing (smaller bore).
The GM truck trannies have a much larger bore hole then the car trannies ball does
The gm car tranny is a smidge tighter than the ford
so it's a matter of taking the front bearing retainer off the ford tranny and having it's flange turned down to fit the gm bell and it's tube turned down to fit a gm throwout bearing
then you take a little off the nose of theinput shaft with a cutoff wheel, dress it up with a flapwheel and install a specially sized bearing in the rear of your gm crank.
You use the gm flywheel and clutch hat and the ford clutch disk
you also have to elongate 2 holes and redrill 2 holes to bolt the tranny to the bell
why do all of this?
If you can find a t19, they are fully synchronized and the ones from a 460 truck or a 6.9 or 7.3 diesel are close ratio instead of granny low with 3 speeds
all ford truck trannies that unbolt from the bell are interchangeable from 1974? to 1989 The only difference being 2 wheel drive or 4 wheel drive.
the early ford 4 wheel drive trannies were either divorced or were 2x trannies with adapters.
I made 75 bucks off a NP435 out of 1970 f100. they has a single speed transfer case so the granny was real low. they are popular swaps with the jeepers and the bronco guys for the law granny
I have a complete NP435 setup out of a 79 bronco I'm going to use to change from a c6 behind my 460 to a 4 speed in my supercab 4x4 project
I also picked up one of those T19's when I junked out a rusty old 1988 f350 but it's a 2x tranny. I need the output shaft and tail cone from a t18 or t19 4x4 tranny to make it wwork in my rig. Being closed ratio and fully synchroed I was thinking just using it in the rat rod.
I also picked up couple saginaw 4 speeds over the years. they used to be spit on but now not so much. I read here somewhere you can install the overdrive from a 3 speed onto them but I never got one to try it.