Hi all I am trying to figure out if I swap my trans with a 700 r4 OD unit what else do I need? I heard the driveshaft needs to be cut or does any company sell these already done? Or am I better off taking the 456 gears out of my 12 bolt posi and get 3 73's ?What rpm does 373 run at 65mph?

 

with a 255/60/15 in the rear, and 3:73s I as running about 3,000RPM at regular highway speeds. overdrive is definitely the way to go.

as far as the driveshaft goes, just go to you local drivetrain specialist shop and they can cut yours to fit. they will tell you how to measure for it, and it will be a lot cheaper than a new shaft. you are better off having yours cut because when it comes to old cars, they are all a little different, so there really isn't anything too standard about them

 

Need your overall rear tire diameter to figure exactly.
Overdrive gives you the best of both worlds.