Great buy! If you haven’t already pulled the pan yet to check for ECZ or EBU on the caps, then take a look at the outer edge of the crankshaft flywheel flange at see if it has a 5/16” raised dot opposite of the half moon cutout. If so, then odds are good that you have a 312 or a 3.44” stroke crankshaft. If there is a small dot or multiple dots, then you have a 292 or a 3.3” stroke crankshaft. If no dot, the crankshaft could go either way.