Slant six upgrade 8 1/4 rear end?

i cant remember the ball and trunion setup off the top of my head. pretty sure you still have a normal u-joint at the back where it attaches to the rear. if that is the case then yes you can use your driveshaft but you will have to shorten it.

oh i dont think i would have to shorten it in the ball in trunion drive shaft goes in and out about two inches