7 1/4 to 8 3/4 Newb Questions

I got lucky today, I found an a body 8 3/4 rear from a 71 Dart pretty local to me at a fair price.

My cars a 67 Dart GT, was orignally a slant car that a previous owner swapped a 273 into. Everything else seems to be original. The 7 1/4 is humming and leaking and I want to swap it out.

I'm taking the whole rear from the 71. 355 SG, with the drums, lines, shock plates and u bolts. I know I will require the the later model brake lines.

The one thing I'm not sure on is driveshaft length. The rear is coming out of a roller with no driveshaft. Will I need to shorten my existing driveshaft or will it mount up to the a body 8 3/4? Any idea how much it needs to be shortened?

Is there anything else you guys can think of that I will need to make this a painless on the ground diy swap?

You should be good to go as long as you have the correct u-joint for the yoke in the rear differential .

Use the driveshaft you are presently using in your Dart.
Yes, you will need to shorten the drive shaft.

Must be different with a Cuda as I had no problem doing this going from a 7 1/4 to an A-body 8 3/4 from a 71 Demon.

As far as I'm aware, that as long as you didn't change the transmission, the drive shaft would work as long as you had the correct u-joint and yoke.

Going from a 904 to a 727 you definitely need a different shaft.