Welcome to the bolt and congratulations on what appears to be an ambitious project. It sounds to me like you have an idea of where you want to end up and the type of truck you want which is great. A few comments as to parts for these projects, you will find everything you need for your type of conversion for the 3100 and nothing for the 3800. IFS, wheels, mounts etc., are all readily available for the 3100 and you can build exactly what you describe. If the 48 is as you describe that is a good buy for the truck and parts. There is a huge market for original AD parts and some of the 3800 parts are difficult to source so you should have no trouble selling off what you don't need from both trucks. Good luck, take lots of pictures and any questions or issues you run into post up here for help.