Welcome..you are kinda local to me. Please pull the valve cover fill tube and look at the rockers. Wondering if they are stock. Does it idle like a cammed car?

3" is a very small pulley. Usually requires a ton of mods to run it and from the looks..your car isn't 3.0" modded. I say this because you don't want to blow up such a nice looking car.

Buickman104 is also in NYC wtih a GTP.