I recently swapped in an 8 3/4 for my 75 duster. (489 case). I know the driveshaft needs to be shortend, I have heard both 2.2 inches and 2.5 inches.

so, since this is a popular swap, how much did everyone need to shorten thiers?

where did you get your "adapting" u-joints from, or did you use a different drive shaft, or some other item changed?

I think it's 2.5
I used to find other driveshafts when I used to do this,
but recently I just had the one I had shortened by a
driveshaft shop- think it was $50. Chances are your U
joints will be fine unless you have the bigger yoke, in which case
you can get a conversion adapter Ujoint (available at NAPA)

I don't remember how much I needed to shorten mine, but it's always a good idea to measure anyway. My 8 3/4" rear has the small yoke for the small u-joints like used with the 7 1/4" rear.

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'68 Dodge Dart 4dr Sedan

I had 2.5 inches taken off of my drive shaft when it was swapped from a 7 1/4 to a 8 3/4 rearend. The shop sent it out to get rebalanced after they shortened it for me. I can't help you on the ujoint question.

I've done this swap twice. 1.75" works very nicely.

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Official Cookie and Mater Tormentor.

okay, so two votes for 2.5 and one for 1.75.

anyone else have some size recomendations?

I have the larger yoke, so I will need the adapter u-joint. anyone know a part number off hand?