i'm pretty sure they will bolt up,
but like sn-95matt5-0 said,they have a different back spacing.
your prolly going to have to call some wheel companies to find out.
but you will need to run spacers.
also i hope you will be changing your rear gears if you get those 20's.
heres a link to a cool gt500 brake and wheel upgrade done on a 94 cobra,might have some info for you.