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

So, I guess I have getting conflicting info on the drive shaft. I read before that I needed roughly 2 1/4" taken out, but is the current drive shaft actually going to be too short requiring a longer one like MoparMike said?
Also, will the U joints be different sizes? Do they make a U joint that will adapt the 8 3/4 to the 7 1/4 drive shaft? I know I had to do this when I swapped an 8.8 into a jeep a few years back.