12 bolt gears from large chev cars will fit in the truck rearend housing. You have to change the carrier also. For example 3 series gears such as a 355 wont fit a 4 series carrier such as a 410. We have a powerglide equipped 66 that we converted from 410,s to 308,s. The ring and pinion along with the carrier came from a 72 chev caprice.
