I am about to purchase a BBK throttle body,
I am not sure if I should get the 52mm or the 58mm.
would a 58mm do harm?I have a 1990 350 TPI

 

What else do you have planned? 58 may be too large for stock, IMO.

 

I want to get a Holley stealth ram and use a BBK with it, right now I have hooker Headers,3" exhaust, and a air foil, today I am cutting out the airbox and buying k&N filters and doin the throttle body bypass. I am also getting 24lb. injectors

 

Go for the 58 but to go larger than stock injectors which are 22 pph, you might have to step up to 26. Those are the cheapest from Ford Racing. You would also have to get your EPROM reburnt since speed density (the system you have) is finicky about adjustments.