I've been researching converting my 1990 F250 from 2wd to 4wd and have found a great deal of info in the forums but it's scattered as far as I can see. I'm going to use the donor method for my conversion and want to build a list of suitable truck-donors (slim pickins so far.. and I want options).

For the purposes of this post the donor is assumed to donate the drive train, starting at the back of the engine (excluding the engine itself) through the tires hitting the road, including the front suspension. The engine, body, exhaust, break lines and other mechanical systems are assumed to come from the original vehicle (though that can vary based on needs). There's good discussions on the forums about DOING the swap once you find a donor here:
https://www.ford-trucks.com/forums/8...onversion.html
https://www.ford-trucks.com/forums/1...onversion.html
http://www.thedieselstop.com/forums/...ersion-212671/

Please add to and correct where needed since this is my understanding from what I've found and I'm no expert (yet, though maybe once I'm done). This info only considers trucks in the 1987 through 1996 model line. In general the best donor is the same vehicle only with 4wd (year, model, engine, trim, etc.).

In general select a donor where:
a) the engine has to match to get the correct mounts of the 2wd truck (same cylinder and fuel type) unless you're changing the tranny as well (see post from L Ward below)
....i) the 300 v6 should use a 300 v6 donor
...ii) the 302 and 351w v8s are virtually identical at the transmission (https://www.ford-trucks.com/forums/2...o-a-351-a.html)
..iii) the 444 (7.3L) diesel should use a 444 (7.3L) diesel donor
..iv) the 460 (7.5L) gas engine should use a 460 (7.5L) gas donor
b) same transmission type (automatic vs. manual) as the 2wd truck

When converting an F150 regular cab to have 4wd:
1- F150 regular cab 4wd pickup from '87 to '96:
2- any '87 to '96 Bronco- I believe all Bronco's were 4wd so that gets easy.

For F250 2wd conversion use a:
1- F250 4wd from '87 to '96 (will need to add the TTB Pivot Mounts however- see post below)
2- F350 4wd same years

For an F350 conversion:
1- Find an F350...

Questions:
Are there specific considerations about the electrical systems relating to the 4wd that should be considered (different wiring)?

 

While anything can be done with a big enough wallet, hammer, or torch, the easiest when doing a 2wd to 4wd conversion, try and use the drive train from the same chassis class, (the only exception being a F250),

IE:

• F150, use either a F150 or Bronco as the donor
• F350 use a F350 donor

The exception being a F250, where you would use a F350 as a donor, rather than mess with adding the TTB pivot mounts on the crossmember

As for the engine, as long as the trans is a 4wd trans, you can do what you want. IE, use a 5.8 engine and trans in a truck that had a 6cyl, or a 460 in a truck that had a 5.8. The key is the transmission being the right trans for the motor and as I said, a 4wd trans.

 

Just to make certain I understand (since my interests are on my F250) if I'm doing a body & engine swap I can use a 4wd F250 as the donor. I guess I'm not sure where the TTB pivot mount fits into the picture...

 

You can use a F250 as a donor, but you will need to add/use the pivot brackets for the front axle on the crossmember below the engine. Since you are already swapping everything over, if you can find a F350, might as well use it for a donor and get the beefier springs and dana60 solid axle

 

So my tear down is getting underway (introduced above) and I hit a snag on the rear axle. Turns out the slowly leaking fluid was from a damaged housing and nota deteriorated seal as I assumed (hoped).

After doing some poking around I got to thinking- since I need a new rear axle why not look for one with disk brakes? It would be newer/better condition (I believe 1999 was the first year with disks on the rear), more plentiful (presumably) and give me a brake upgrade at the same time. From what I can tell the 1999 through 2004 super duties used Dana 80 rear ends (true?). My question is pretty simple- can I take the Dana 60 4wd front axle and Dana 80 rear from a 1999+ super duty and bolt them under my 1990 F250 conversion (discussed above)?

And yes, I realize it's easier to buy a new 4wd truck, with full disk brakes- ease and finances are not my main drivers for the project...

Oh, and since I'm here I'm also adding a link to "Project Responder" which shows a pretty friggin cool rebuild and modification of an F250:
Project Responder, The Ultimate Volunteer Fire Fighter's Emergency Response Vehicle

 

You will also need the later model wheels (different bolt pattern) and I "think" there is also a difference in the width/position of the spring mounts on the axle tubes.