A lot of my firends have T25/T28 style turbo's. You could have the standard be the T3 flange and maybe offer the less common flanges for a small fee increase? Say, 20 bucks or so? Most people would understand that there would be a waiting period if they needed a less common flange installed instead of one sitting on the shelf already.

I'd just offer a wastegate blockoff kit for those who wouldn't need one. Most people WANT to go with an external wastegate setup down the road anyways so they'd like the possibility to be there in the future.

Jamie-
-AUTOMATIC turbo'd 95 Talon ESI@8psi (stock internals)14.0sec=1/4 mile

-2003 Mitsubishi Evo VIII