The engines are totally different, I doubt there's a single component common to both (save for some of the nuts and bolts).
For starters, the block was redesigned and is a seven main bearing unit that is about 1.75" shorter. The head doesn't breathe as well (I'm pretty sure the valves as well as the ports are smaller).
And it just doesn't rev like a proper Healey!
Edit: the redesign came about to comply with upcoming emission standards. Ironically the saloon that the engine was destined for didn't fare any better.
The performance (or lack of) was the MGC's downfall. I think the handling could've been worked out, but without the "scoot", nobody wanted to try (okay, John Chatham is the exception).
[ 01-05-2004: Message edited by: Randy Forbes ]</p>