Not sure if many would know but can you use a rear 3rd member in a solid front axle. Its the same size ring gear and same 30 spline as the rear axle

 

Yup direct swap, once upon a time I had an 84 with a rather stupid 355 in it with anywhere from 35's to 40's on it and I'd blow the rear gears regularly. If I didn't have another good 3rd on hand I'd pull the front one and stuff it out back. When I finally traded it off it was running #11 and 12 3rd's.

 

Is the brake lines for the 7.5" rear and the 8" the same? gonna be swapping rears out soon would hate to have no brakes in the rear