I have a 92 F160 standard cab 300 six 5 speed, it's a work truck and it gets to work hard. Never dump the clutch, try to get moving without rear shudder as much as possible. For months there was a sound coming from underneath somewhere like a vehicle that's been stopped too many times by putting it into park while still moving. Obviously that is not the case, as it's a manual. a couple weeks ago it made a loud BANG noise and felt like it skipped a tooth in the rearend, so I took it easy and got home. I went to drive it again and within a couple of hours it did it again, twice in a minute. Both times with a bit of a load, but not really heavy. Maybe 1000 -1200 lbs. I made it home again, but it is doing it every time I try to move it out of the way. SO, i bought a 95 F250 extended cab, 460 auto with a blown head gasket. I will be driving it home tomorrow (about ten miles) I originally planned to put the diff into the F150, then decided that since I regularly load as much as 1500-1700 kg on it, and there's NO room for my tools, I will be far better off to put the 300 six 5 speed into the F250.
Now for the 50 questions;
Which driveshaft/ u-joints? Will the F150's air bags work? Can they be used with a pair of overload helpers I saved from the last 1990 F150 4x4 parts truck? Where would i add to the stainless Magnaflow cat back system, I assume the easiest place is right behind the cats? Will there be any wiring problems?
Due to unrelated uncontrollable circumstances, at this point I am almost broke with two other projects unfinished and on hold because the work truck comes first. This is the sixth or seventh truck since I started hauling for myself, and I always got the next truck before the one I was using would break. In about eight years I have only been broken down for more than a couple of days once or twice. (same goes for the trucks) It's been a bit over two weeks this time, and the holidays are approaching and I have two kids. (ok, they're teenagers, but ya know it is looking rough right now)
I need good news
Last question, how do I find the answers to my questions? How do I find THAT answer?
Oh, this is not looking good.

 

Your problem may be in the transmission - the 5 speed behind that 300 is a light duty Mazda box which is known for input shaft issues. I wouldn't try to use it in a F250.

If you want to do the swap, I'm sure it's possible but there are going to be a lot of little issues, including wiring and electronic issues.

Honestly - I'd put head gaskets in the 460 if you want to use the F250.