Probably not too hard if you look around. For an NA build on a GSR or ITR though, people will often just use a B16 head, CTR intake cam, ITR exhaust cam, and CTR pistons to raise the compression. Without going aftermarket, this is an incredibly potent setup.

 

on a turbod car would it be worth it to look for a CTR head?

 

Nah. Especially since the B16 or ITR head will work equally well, if not better (give it up for factory P&P!).