04-06 S4R/S4RS exhausts interchangeable?

[hyphen]

Are the exhaust setups (full or slip-ons) interchangeable between the two bikes?  I assume they aren't, but why aren't they?

[MotoCreations]

S4 and S4R have two exhaust ports (ala 916/996) and thus a 2 tubes into 1 header.  S4Rs (Testastretta head) has one giant oblong exhaust port shared by both ports which is @33.5x54mm and the header goes from oblong to round tubing. (not fun to replicate for aftermarket exhausts)  Also the exhaust ports are in a slightly different position in terms of x-y-z axis.  No way possible for a full setup to be interchangeable up to and including the udder. 

Slipons that go from the udder back are probably interchangeable between both bikes.

[hyphen]

ahh, thanks for the clarification.