66 slant six fit my 72 slant six tranny

If it really is a 66 engine the hub at the rear of the crank is to small for a 68 and up automatic torque converter. If your using a manual transmission just use the flywheel that came on the engine. 60-67=1.95 diam 68 and up = 2.15 this is the size of the lip the flywheel or flex plate sits on

Brian