Depending on what front differential you chosse, if you go with a stock Toy 8" (passengers side diff) or a D44 with a passengers side diff, then your stock drivetrain is fully compatible since your IFS is also passengers side diff.

As for the differences,
The bellhousings are different. R150F uses a bellhousing for a VZ-family engine and the R151F usea a bellhousing for a R-family engine and it has a hole at the bottom with a rubber plug, the R150F's bellhousing does not.
The tail housings are different. R150F uses a tailhousing with a boltpattern for the VF1A chain drive t/case and the R151F is for the RF1A chain drive t/case.
The shifter socket, selector, and selector shafts are also different between the two.
The output shafts are the same.
1st gear is different. R150F uses a 3.83:1 first and the R151F uses a 4.31:1 first gear.

That should about cover the differences until Marlin comes in here and really start throwing around some numbers