flyinghigh2k8

I have a 95 mustang gt and want to start on some mods. I already have a cold air intake and what to upgrade thr thottle body. My question is does it matter what size I get. I've heard that generally bigger is better but I think you have to have the rite size headers to match it. Could somebody please explain to me about throttle bodys and what I would need to modify to get one.