Catalytic Converter Query

[rapidtornado]

Not a whiz on all things exhaust so thought it best to ask the experts....

Taken my exhaust off the donor this weekend, the cat conv looks a bit bulky and I was wondering if I could use a cat from a different vehicle on the roadster instead of the donor cat?

I'm just wondering if the cermaic honeycomb is specific to the car or is it age related i.e. I could take the cat off say a rover 416 and use with my twinky engine

Any advice would be appreciated as always

Cheers
rapid