confused about a drum/disc swap

[Hottrucks]

ok heres what I have and was woundering what the results are going to be...

I am looking at a 71 truck with disc I want to keep my cupped LCA from my 70 ( I know I need to swap the ball joint )


what else do I need from the 71

will it wided my wheel base how much?? (worried about fender lip clearance with my 8" rallies when I drop it)

Is there a stock 6 lug disc that will go on the 71 spindle?? or do I need to find new wheels and swap the rear axles??

I plan to pro street the truck in the near future so I don't want to start playing the tire/rim 5 or 6 lug game I have plenty of 6 lug 16 hole rallies and was planning to cut and widen one set for the rear....is the 71 axle narrower if i have to do the 5 lug thing??