The verdict is in... I am going to get a Holley Stealth Ram for my IROC. However, I am not sure if I should stick with the stock throttle body, or upgrade to a 52mm or a 58mm.

My motor is a rebuilt 350, .030" over
083 heads opened up to 2.02/1.60, screw in studs and guides, etc.
CompCam 264/274 .480/.480 cam
CompCam 1.52 roller rockers
Hedman shorties
Accel remote mounted super coil, 8.8 wires
Will also be running an AFPR

Any suggestions on throttle body size?

Thanks!

 

A 58mm leaves a lot of upgrading possibilities with the car for making more power. I am about to change from a 48mm to a 58mm on my HSR and I will let you know how it does.

 

my combo with the stock 48mm on it shows 4.58v on the map at wide open throttle 5800rpm and 4.66v at no vacuum. This was checked with no air cleaner on, with the stock firebird air intake on it was 4.14v. So with your combo being a little more mild on the cam I'd say the stock throttle body with a good air duct would probably be just barely enough. If you're going to buy one I'd just get the 58 and know that it was more than enough.