7 1/4 to 83/4 swap - A Body

Ok, I'm looking to buy a 8 3/4 open diff from a forum member to swap out my 7 1/4 for.
What can I expect during this swap?
Will the drive shaft need shortened?
Will the U joint sizes be different?
Will my 14" rallyes fit or will I need to look at 15" due to larger drums?
Any axle width differences?

I am trying to keep this as straight forward as possible.

Thanks FABO!

Clark