Will a 1969 gto rear end fit a 1971 Oldsmobile 442?
Yes...the dimensions are the same. The only difference may be the type of U-joint used from one car to the other. Otherwise, it should be a direct swap.
The Oldsmobile 442 means (400 cubic inches-after '65) (four barrel carb) and (dual exhaust) if your car does not have these it is not a true 442. The 350 that year had only 160hp to 180hp but the 442 should have had the 455 and 270hp to 300hp. Are you sure your car is a 442? It may be a cutlass with a 442 paint job.
The factory provided only 400 CID engines in the 1965 thru 1969 442's. The 1965 thru 1967 400 engine [block casting ID "B" (1965) or "E" (1966-67)]had a shorter stroke and forged crankshaft; it was basically a 425 with smaller pistons. The 1968-9 400 engine [block casting ID "G"] similarly shared the crankshaft with the 455 then available- a longer stroke- which means the '68-69 400 pistons were much, much smaller diameter, for a markedly…
Olds never had an engine that displaced 442 cubic inches ( common mistake ) 442 was a model or option designation depending on year built engines available were 330/400/350/455/ Later on 307 General rule of thumb you gain about 2 cubic inches for every .10 over. Example 455 at .60 over would be about 467 to 468 cubic inch engine