A friend gave me a 700r4 out of a 82 Chevy PU. I had it rebuilt ($500) plus I bought a new torque converter. My question is as regards the length of the driveshaft. I know it has to be shortened. Do some of you folks know the exact length. The differential is a 10 bolt (non-posi.) I bought a new crossmember from Bowtie Overdrive. Thanks for any help.
Mike

I would install the trans, then measure from the center of the rear ends pinion yoke forward to the outer lip (seal) of the trans input. Take those measurements to the driveshaft shop. They'll know how long to make it so that the trans yoke is at the proper distance to fit properly.
There are other methods I'm sure, but this will help build a driveshaft that fit's your car and particular setup perfectly.