Hmmmmmmmmm... back to thinking on this. It APPEARS that the manifolds will just swap over no sweat.
Timevalve shows that the Euro duals (not Tri-Ys) will fit the 500 and 380.
http://www.timevalve.com/cat/euro/p26b.html If so this will be nice. I'm know the the Tri-Ys will make more power but heck, at $25 I can't beat the others.