Ita a manual trans thing, all convertors used the same ring gear diameter. thats why you see 8 inch race convertors with the ring looking like a hula hoop on them. BUT all convertors dont use the same center register. The early 273 convertors used a smaller register than the later ones so you need to run a bushing (like a pilot bushing but thinner) in a later crank with an early convertor. Itll bolt up fine, but youll end up breaking the flexplate, BTDT.