Here's my situation. I have a 383 motor that I'm not using right now so I thought I'd look around for a third gen to throw it in for a while. However, I also have 12 bolt 4.10 rear axle on a 75 Chevy truck that I'm not using I was wondering if this will simply bolt right up to a third gen? I've heard that it is actually easier to swap out the entire rear axle than it is to just do the interal gears. Also, can anyone tell me what kind of RPM's I would turning around 70mph. I'll be driving the car on highways almost daily so I don't want to have to rev the **** out of it. Any advice??

 

If it's the same width which I doubt, you would still need to cut and weld all the panhard/shock/spring locations in the right spot. Then you have to fab up a way to mount the torque arm.

 

I am curious about this swap also. The aftermarket rears are too expensive. Guys were fabricating 12 bolts and ford 9s into 3rd gen before the aftermarket ever caught up. I just wish I could get more info on the swap.