I'm not referring to the bolt holes on the pressure plate, I meant you should measure the diameter of the face of the ring that actually contacts the disc.
Now we know why you're having starter problems. You need a mid 50's V8 starter for that bellhousing.
The bell isn't really for a 292. Makes me wonder about the flywheel. If the flywheel is from the same source as the bell, then you could very well have a 10" clutch.