170 or 225?

Best way to tell there is a pad on the block behind and under the alternator that sticks out JUST under the head. There are some stamped numbers on it that will include the engine size.

And I know this is an early car, but the bypass hose thing only denotes short deck (170) or tall deck (198 and 225) so it's possible it's a 198 also if the bypass hose is about 3 or so inches. It would have had to be swapped in of course, but a lot of time has passed since that car was new, so you never know. The pad behind the alternator is the best way, UNLESS you're a contortionist and can bend your way under the intake and exhaust manifolds and get the casting number off the driver's side of the block.