stock exhaust diameter...

does anybody know the diameter of a stock exhaust??? im thinking of replacing my header while i am rebuilding my engine but i dont want to do a whole exhaust. the header im looking at says that it has a 2" outlet, will this bolt up the stock exhaust or will i need to weld some diameter converters?

that will bolt up the the cat.

stock diameter is 1.85", shouldnt make much of a difference when bolting up to the cat.

k, thanx guys