Driveshaft length

Is there a difference between early A body (1965 Barracuda) and the later A bodies when it comes to driveshaft length? I would imagine wheelbase has an influence on the length. I have a 65 Barracuda that is getting a later model 904 and an 8 3/4" rear end. While on the subject, what is the best u joint size to use? The engine is a rather healthy LA (~400hp at the crank) and yes, on occasion I use that hp. (hence the 8 3/4) If anyone has done that swap - a rather common one, I would think - I would certainly be thankful for any information on the driveshaft specs!
Thanks
Cheech/ Art/ R/T