Is that a an 'SR' block = 1970 GS 455 (non-Stage) engine. All Stage cars were built in Flint in 1970 ... other plants built them after 1970. J2 Forced Comfort-Flo ventilation - don't see that option very often. My bad Van, it is an 'SF' block (from a full-size '70 Buick?) ... letters start running together at 1a.m. ...
Looks like SF code on the block. Rear control arms are not boxed. I don't see 12 bolt on the Differential cover. Rear quarters have bondo in them. Front fenders are rotted on the bottoms.
I only counted 10 bolts....I like the Olds W27 rear end cover, though. All in all, it looks like a great driver, and you don't have to worry about blowing up the original engine. Dan