Re: 1967 belvedere claimed as a gtx.
 

Speaking from experience... If you take the 906 down to closed chambers, it's not a matter of if they will crack between the cylinders, but when. I suppose in a Stocker though, cutting the surface down to 74 cc, it's still going to leave a little of the chamber in the head.

Paul is pretty close on his numbers. The last 906 I measured was 85-86cc, and I know it had a light cut. If I was going to cut an open chamber head down though, I'd use a 452.

Re: 1967 belvedere claimed as a gtx.
 

There are two versions of the 915 head, the GTX got the 915 HP head which has a larger exhaust valve . If you are having problems finding 915 heads , Mopar also used them on the marine version of the 426 wedge in 1968.

Re: 1967 belvedere claimed as a gtx.
 

You canput 1/75 Valve in the 1.60 Head.
You are not going to run stock valves anyway.

The 1.60 head fit more applications that are run in stock
currently.

The 1.75 Heads have HP stamped on the front flat surface.