Valve reliefs are in stock locations. 4x heads were on it I am not sure if these are the same angle as the 6x. Thanks for the info. I will have to figure that out
Yes, 4x & 6x heads have the same angle. But, again, the 389 reliefs are in a slightly different place than in '68-up 400 pistons. And, the valves in the big chamber heads may be slightly further from the pistons--don't know. If so, the same cam will put the valves closer to the pistons, when using the smaller chamber heads. Valve distance from the head surface may be the same, with just a bigger chamber. I suppose the difference(if any) could be measured, with accurate measuring equipment.
Better to measure & check things BEFORE ordering parts.
"...Ran a Com Cams XE262 and a XE268..."
Most Pontiac engine builders do not recommend the XE cams. In fact, the CVMS guy is the only one I know of. For low compression builds most recommend the Voodoo cams, instead. They supposedly shut the valves more gently, making less "valve slap" noise, than the XE cams.
No, I've never run any of these cams. Just passing on info. You can search the PY site, or ask them about the XE cams & get lots of opinions.