Mark,
Don't know for certain if it's interchangeable with another car, but you most certainly will not find it new unless you happen upon it on eBay.
Brown & Gammons, Moss, VicBrit, AngloParts - they don't even list it, or almost any other British car clutch forks for that matter.
Best source used would here, the BB at
www.mgcars.org.uk on the MG Experience MGC Forum. Also try some of the larger used British car parts places - Atlanta Imported for one.
I know of a few people who have lots of MGC parts, and they might have it. Reply back to me at
mgcsaylor@comcast.net.
Just curious - where's this C from?
Mark A. Saylor
Editor, American MGC Register