TB Size, 75MM Intake Not 75MM

Hey, so I just got a street trick flow intake, and it said the intake size was 75mm, but when you measure it, it is more like 70mm, so when buying a tb, should I buy a 70mm, or should I buy a 75mm, will the 75mm tb actually be 70?

Thanks

Emissions 347, Street Trick Flow Heads, Intake, Powermax 2030 Cam, 1.6 rockers, 30 lb injectors, 80mm mass air meter. TB??? EGR Spacer???