Should all be pretty much bolt in. The change in wheelbase will require drive shaft length changes.

 

You will find 2 wheel drive frame is a quite flimsy compared to 4 wheel drive frame.

 

I don't dispute that the 4x4 had a slightly heavier frame but I wouldn't call a 2 wheel drive frame flimsy. Lots of guys, including me, have converted 2WD trucks to 4WD and prior to the factory 4x4s in '59 all of the 4x4s were converted 2WD trucks.

 

My '66 f-250 2wd frame looks just as heavy as my '79 F-150 4x4 frame all the way back to behind the front spring hangers, then it tapers down a little smaller, but still plenty beefy. I wouldn't hesitate using the 2wd.

 

Yes, but yours is an F250 so it's not the same. IIRC, for some reason I am thinking that pre '66 F100 4X4's and F250 4X4's used the same frame which was very similar to an F350. F100 2wd's were far and away lighter and I have no idea about F250 2wd's.

Personally, I would not do it.

Now if you wanted to go all out and prep and box the frame and add a few welded cross members, I'm sure it would be strong enough.