I run a Pontiac 455 with a turbo 400 in my '68 Firebird and it is a very quick car. If it needs rebuilding, you could build the similar Olds better, and take care of the oiling problem.
These motors can approach 600 lb-ft and reach at least 1 hp per ci if you improve the compression, cam, intake, and exhaust.
The 455 is probably the greatest truck engine they never put in a truck.
