Usually, somehwere in the item's description, it'll tell you which kit it's for. Eduard, for example, is really good about that:
http://www.eduard.cz/
http://www.squadron.com
Tha being said, almost everything out there you're going to find in the way of aftermarket (for 1/48 kits anyway) is going to be specifically for Hasegawa's F-4 kits. There may be generic F-4 bits you can use on your T/I kit, but, in general the parts are designed to fit a specific kit.
Well, I just checked Eduard's site and everything they've got for the F-4E/G is for the Hasegawa kit. Keep your eyes peeled and ask around some more, eBay may even be woirth keeping an eye out for it.