For 1970, General Motors dropped the internal rule capping intermediate cars at 400 cubic inches, and Chevrolet answered with RPO LS6: a 454 rated at 450 horsepower and 500 lb-ft on 11.25:1 compression and a solid-lifter camshaft. Roughly 4,475 Chevelles got it, and it lasted exactly one model year in that car. Whether any particular survivor is the very last one built is a far harder question. Read on to find out why.