Hey guys. I've got a 78 F100 swb 2wd with a C6 automatic that has crapped out. Planning on a rebuild. However, I found a C6 Heavy Duty auto from a 91 with the 300. Should this be a routine swap or is there a modification that'll need to happen? Your thoughts are appreciated.

 

I don't think there would be ANY difference at all between the two, aside from internal improvements throughout the years.
It should be a direct swap.

Just make sure that you get the correct 2WD/4WD configuration as , as far as I know, they're not interchangeable.

 

Thanks for the info. That sets my mind at ease.