Does anyone know the stock diameter of the throttle body and runner holes on a TPI plenum (out of an 85 305)?

Ive got the plenum ready to polish it and I want to see if it has been ported since the previous owner installed aluminum SLP runners and an aftermarket throttle body.

Also, I have seen cases where people have (successfully) ported their own plenums using a sharpie marker as the outline and a dremel tool for the porting. Will this work fine if done right? If this can be pulled off I'd much rather take the DIY route than send the plenum off to be ported.

Thanks.

91/92 model:

TB larger part is around 2.03
TB smaller part around 1.875


runner ports around 1.59

I meant the throttle body holes in the plenum not the actual throttle body.

Thanks for the runner diams though.

That is the plnium size. I have one laying out in the garage.

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