Hi All-
I've recently acquired a 1965 f100 4x4 with a well worn 300 straight 6 and 4 speed thats pretty stock. I've been trying to reasearch motor and transmission swaps but have been coming up empty handed. Clutch work is hard on a bad knee so my goal is a bigger motor and an automatic transmission trying to leave the original transfer case so I only have the one drive line to adjust the length. Was thinking 351, 390, or 460 with a c6? If the truck was 2wd the swap seems pretty straight forward but I can't find anything on doing the swap with a 4x4. Anyone have any experience doing this or any direction they can point me? The more bolt in I can make this the better it will be for me as my welding skills are garbage. The only other option I could think of was to find a 70's 4x4 with the drivetrain Im looking for and do a body swap?

Thanks in advance everyone for your input!

 

If I ended up leaving the original transmission and replaced the 300 with a 390 would it bolt up? Would I just need a new bell housing for the 390 or are the bell's interchangable?

 

Why not rebuild the 300-6. They are great engines and alow mid double digit fuel mileage numbers.

 

It is a conglomeration of parts. What does the vin tag say? Looks like a 3/4 ton chassis that has 1/2 ton front spindles or axle. I agree with co425 on this one.

 

Old post, so I don't know if the OP is still watching. But if you are...

The 300 six has a devoted cult following. Personally I'm intrigued by it and will probably get one at some point. But if you want "a bigger engine", that ain't it, you need to go with a V8.

For engines, from what I've heard the 390 is a good one, but is pretty old, which might limit your trans options. Same with the 351M (except for the part about having heard it's a good engine). The 351W and 460 are both newer and good engines. It just depends on what you want there.

For an automatic trans, you can probably get a C6 for any of those engines, but with no OD or lock-up your mileage will suffer. You can get an AOD for the 351W to get OD and lockup in a relatively easy trans to set up, but it's not necessarily the strongest trans if you're going to beat on it. Or you can get an E4OD for the 351W or the 460, a strong trans with OD and lockup, but it's electronically controlled so it requires a controller.

I don't know how you hope to only change one driveshaft by keeping your original t.case. Your going to have to lengthen one the same amount as you shorten the other. But then again, I don't understand why most people on this site try so hard to avoid changing driveshaft lengths. it only costs about $125 per shaft at a shop.

Oh, I suppose if you currently have a divorce-mount t.case then you would only need to change one of your three driveshafts (as long as the new engine/trans isn't too much longer). In that case you'd need a 2WD version of whatever trans you want rather than a 4WD version. But I'd think that overall it might be simpler to go with a new t.case.

If you do keep your stock trans you might want to seriously consider a 351W. That'll bolt up to your stock bellhousing. You'll still need a new flywheel and possibly clutch, but the rest should be pretty easy. If you go with a 390 you'll need a new bellhousing as well as the flywheel and possibly clutch.