i bought a pair of 2.5" magnaflows for my z34 but i still need to buy the adapters so i wanted to make sure the stock exhaust is 2 1/4" before i go out and buy them. i tried to search for it, but i couldnt find anything. thanks

 

yep its about 2.25 why not have a shop just install them? they can stretch the metal and you wont need a clamp or adapter

 

A shop is the best bet for that. Much less chance for injury and you are having a pro do it.