Hey Chris,
Thanks, let me find out. Mike Mackaman had some info about that on the site somewhere. I'll PM him and see if he knows.
Oh, wait, duh.
The 260Z has the larger exhaust value. The 240Z had a 1.65" intake and 1.3" exhaust. This valve size stayed the same till the 260Z when they went to a 1.38" exhaust ( same as the 280). So, if the exhaust valve measures 1.38" then it is, more than likely, a 74 E88 head and legit for a 260Z.
I need one. Fresh out up here in NC. If you have one for reasonable money let me know. I can arrange the shipping part so it is painless.
Thanks,
Ron