Stock style 3 bolt turbine housings are set up with the additional port for the wastergate puck and actuator. Turbonetics has custom turbine housings set up with an integral Deltagate flange. 4 bolt style housings would require the Deltagate or similar style wastegate to be mounted elsewhere (such as the header or crossover).
My question is why are you switching? A stock style wastegate is good well into the 10's. For an 11 or 12 second car, you will need 2 Deltagates to avoid boost creep.