New to mopar 8.8 swap

Hi guys I'm very new to the whole mopar scene and I recently purchased a 70 Duster. Im in the process of stripping the whole car for some body work that needs to be done. Im also pulling the /6, 833, and 7 1/4. I'm hoping to put in a 440 with a 727 and looking at rear end ideas. Im also mini tubing the car with a spring relocation.

I understand the purists will crucify me for doing this but I just can't see spending the kind of money to do it with an A body 8 3/4. I have a few questions, I've looked at the sticky and its answered most.

1. How would I go about measuring the correct length to take off each side with the mini tub?
2. How would I go about shortening the axels, and if I can't do that where would I get correct length axels?
3. What kid of offset are people running on axels that are mini tubbed for a 10 inch wide wheel?
4. How would I set the spring perches in the right spot on the new shortened rear?

Sorry if some of these questions are stupid/ have been answered already like I said I'm very new to this whole thing and don't know where else to look.