No, a complete Chevy rear end will not fit a 1970 Oldsmobile Delta 88 without significant modification, and likely not even then in a practical way. The bolt patterns, spring perches, and overall width are different between GM's A-body (Chevy) and B-body (Oldsmobile Delta 88) platforms. The housing width is a major hurdle; B-bodies are wider.
While some components *might* be adaptable with custom fabrication (like axles or differential itself), it's a major undertaking and not a straightforward swap. It would be far simpler and more cost-effective to find a suitable Oldsmobile or even Pontiac rear end for the 1970 Delta 88.
