I just read that Buick GN and '80's model 442 Olds had 8.5 "G-body" rear that might bolt in to a '79 Lemans.
I assume these are rare & expensive nowadays.
Here's one on Ebay for $950--pick-up only.
http://www.ebay.com/itm/1986-1987-bu...-/191975356459
I assume a '78-'81 Lemans would be considered a "G-body", even if they were still called an A-body when they were new. So, I suppose that means any G-body rear from '78 to '87 or so, would bolt in. ???
Here's a complete 9" Ford G-body rear, for about $2k. Might be a better buy. You could even have 2 chunks set up--one for street cruising, one for strip time.
http://www.ebay.com/itm/9-Inch-Ford-...-/391407302983