That's a beautiful Buick. I had the same rims, just 3.5's on the front. We could pull small wheel stands from a light with good pavement thanks to the wrinkle wall Hosiers.
I had a bunch of KB, Dutweiler and Lawrence Conley crap on it.
Some of what I can remember: Art Carr 400 with a 5k stall and brake, custom crane cam, aluminum heads, Giant Garrett (can't remember size) with wastegate dump out the fender, 2-286 fuel pumps, front mount intercooler, injectors, etc... Very quick on AV. I can't wait to see more pics of yours.