[americanmusc1e]

After coming to understand your situation some more I think the best thing that you can do is first find the shop that is going to build the truck and seek the opinion of a professional.

You completely specing out a vehicle based on the opinion of different people on the internet is a bad idea. You want this to be new vehicle quality and imo the entire key to a perfectly functioning and reliable vehicle is that the sum of the parts add up to much greater than their own merit. In other words, the best parts in the world, if mismatched will be no better than properly matched mediocre parts. This one internet thread cannot supply you with near enough information to make a good decision, and taking ideas from totally different people and mixing them together will also end in failure. As a novice you would need to spend a couple months researching this to understand it enough to get a good idea of what you need.

A better idea would be as follows: Ask around on here for recommendations on good local shops. Pick a couple of them and call them with your plans and see what they say. Then post the results back here and we can help you sort through them.

and to answer your questions.

semi-float axles are used more in half-ton applications. they are relatively weaker than full float, can be harder to replace parts on quickly, but they are lighter. Full float have the additional advantage of putting no weight on the axle shaft itself. In the end the choice comes down to the tire size and intended use.

You can make a 10bolt strong enough for this application. the weak link on the 10b front diffs is the axle joints and axle shafts themselves. there are aftermarket HD replacements, but they cost as much as replacing the axle with a D60.

as far as 14bff vs D60 rear. It really doesn't matter. the 14bolt is cheaper and easier to find, but a D60, D70, F0rd 9" or Eaton H052 would also work just fine.