Questions for 8 3/4 swap

Hey guys! I'm just about to swap an a-body 8 3/4 into my 69 dart. I just picked up new u-joints, shocks, and u-bolts. I've tried to do some research on the internet for full details on the swap but haven't had much luck.

Without having taken measurements I'm curious if it will bolt right in?
Here are my main questions:
Do I need to shorten my drive shaft?
Do I need to relocate my spring plates?

Here is another question I have about the rear end:
I've heard good things about floating axles, are there any good kits for the 8 3/4?

Thank you for your help