If you use 78/79 with cast wedges I think you will need to space the buckets out about 1 & 1/2 inch to 2inches.
Outside steering box will work fine also, just seems they cost a little more than 1st gen.
Stock Radius arms can be extended and that should work for you.
As far as axles go if you can swing the $$$ the best setup would be to buy a Dana 60 King pin axle, I believe certain Ford trucks from 79-91 Had these, forsure 86-91 4wd F350
If you were able to go that route u shouldnt have to ever worry about axle strentgh with 37s so when you are ready to push the limits your rig is ready other wise stick with Dana 44
As far as rear axle goes, I would prolly stay with your disk brake 8.8 and just run adapters that widen and change bolt pattern.
I think I remember also thinking front drive shaft didnt look like there was enough room for droop without hitting the cross member, but mine never did, but I had atlas 2 behind M50D, whereas you have the Auto and I assume 4406? So not familiar with how it sits in there.
*********Now if we could only convince that Turdle guy

to do the same, thing****