[1968SWBBigBlock]

Truck & car units are not the same. The bearing carriers are different. The unit that is on ebay I would not touch. Truck units came in 3 sizes, 2 series, 3 series and 4 series. 2 series handle 2.73 gears, 3 series 3.08 - 3.55, 4 series 3.73 - 5.13. Any truck 12 bolt carrier will work in your housing, it depends on what gears you have to match the center section/posi unit. If you buy a second hand unit series 3 center section you can get extra thick gears on the 3.73 and up gears, this would allow you to run a 3 series center section with the taller gears. As far as the GM units not being any good. GM used alot of makes over the years, Dana was used in the 4x4's, Detroit was used in the 14 bolt rears in the 90's but Eaton has produced the largest number of units for GM. I have spent alot of time the last 3 months researching center sections and the common theme that came from 99% of the folks that build rear ends or sell rearend products is you can not beat the Eaton units. FYI the Moroso center section is a heavy duty Eaton unit. Not reccomeded for street use.
When you go thru your rearend make sure and buy 2 bottles of Posi lube not 1. Your center section will thank you for it.