I currently have a 1975 Ford F-250 highboy with the full time setup. It has a rebuilt 390/C6 combo that I'm really happy with. Now I want to upgrade the rest of the truck (powertrain wise) so I have several questions on what the best rout would be to take.

1. I understand that a Dana 60 is one of the best ways to go to replace the stock dana 44. What year axle should I look for and what should I avoid. Something that is really easy to install would be a plus too!

2. I want to lift the truck about four inches and install 38 inch tall tires. Who makes a good lift kit that's not weak but won't break the bank (part numbers would be appriciated). Keep in mind that the lift will have to work with the swapped in Dana 60 front axle.

3. What is a good gear ratio to swap in the axles with the mentioned tire size? I want to also do away with the full time t-case and put in a doubler kit.

Any feedback would be greatly appriciated! Thanks!

 

http://77cj.littlekeylime.com/Dana60.htm

 

Good link from Dennis, so hopefully that takes care of question #1. It should mention to stay away from early model 60's with a low pinion. You will try to find a 60 from a 79'.
Most, alright maybe not most, some of us are running Super Duty front springs on our trucks. I use a 4" spring pack, and a 2.5" hanger kit from a Super Duty truck, and it works, and drives well.
That gear ratio question is a tough one. This will depend on your intended use for your truck. A 38" tire with a 1.1 output wil net approx 1900 rpm at highway speeds. Maybe that is cool for you, and maybe not. I might prefer a 4.56:1 with a 38" tall tire, others might say that a 4.11 would be alright. You will have decent low range with the doubler setup. Doing the doubler will require some work, you will have to marry the current 203 to the transmission, and then find a 205 that is also married (with the right input splines), buy an adapter to bolt them together, make a new crossmember, make, or buy shifters to shift everything, and last but not least, make new driveshafts.
As an example, I run a doubler with front and rear 60's (Detroits at both ends), 5.13 gears, and 39.5" tires. I run rocks, big ones, and the lower gears in the diffs, combined with the doubler, gives me many, many gear options. You will just have to find the combo that is right for you.

 

I too want to be able to run through the tough stuff but still be able to drive it on the highway at a decent rpm. So a Dana 60 from a 1979 one ton 4x4 would be the thing to use. What did you use in the back, or what you mentioned was used all the was around for the super duty lift kit, 75F350?

 

If you are asking me about my rear suspension. well this is where thing get interesting. I use a stock spring with a 2" AAL from a late model Chebby truck. The spring is super long, and allows for much flex. I had to relocate the original hangers, and did a shackle flip while I had everything apart. I works well for me, and is strong. I also use some half leafs that I had from an old eliptical set-up I ran. I used the half leafs to reduce axle wrap, and help prevent axle hop under hard acceleration, while still allowing plenty of flex.
For the front axle the 79' D60 is about as strong as you will find without getting into custom stuff. The stock axle has 35 spline inners, and probably need to have the outer shafts upgraded to the same 35 splines. This is a proven combo, and is very strong. If you outgrow that, then you will step up to chro-mo axles, and heavier duty u-joints. If you start breaking that, then you are one bad dude. I get plenty of criticism for still running a D60 in the rear of my truck, but it works for me. The way I see it stock stuff is pretty stout, and a D70 is stronger, but in stock form, not as strong as my 60 with 40 spline chro-mo shafts. I have a bunch of money in these axles, and don't really want to start over again. I am hard on my truck, and it survives beating after beating, and keeps coming back for more. I hope this helps a little. If you are looking for details too long for this reply, feel free to PM me. I will be glad to chat with you.