The external parts like the exhaust, water pump, alt etc on the N/A and SC interchange as long as they are the same type. In 99 most have the newer style alt and bracket where the alt bolts in from above but some still had the older style which will not even bolt in so that would be a no for interchanging them.
As far as internals go some of the parts will be the same but only way to tell for sure is to take them both apart and compare. Dan
[This message has been edited by FIEROFLYER (edited 12-24-2013).]