I found this on Craigs list. https://detroit.craigslist.org/okl/pts/d/farmington-gm-rear-end-differential-10/7056085648.html I spoke to owner. He still has it. Says its a 10 bolt posi from a 1978 Trans Am but he wasn't sure of the gear ratio. He said he thought it was a 2:73. He said it was the OE rear end. He says it is in excellent condition and it does look pretty clean in the pics. I did some searching and I dont see where the Trans Am came with a 2:73 posi. From the info I found it looks like it "could" be a 3:23 or 3:42 with a Pontiac "Safe T Trac" type limited slip? Any one here know anything about what rear ends came stock in the 78 Trans Am? There are casting numbers included in the pics. But its all greek to me. I'm considering this to put in my 78 Type cause it would save me some money. Just not sure if its a good investment. I was really looking for a true trac type posi and going with lower ratio like 3:91. I'm going to be running this behind a 4l80E trans and stock LS3.