Can you see if there has been any work done to my heads?

66fs said
Yes, they have been ported or at least gasket matched from what I can see.

Thanks, as I suspected then.

teringer said
it looks like you were running a 340/360 intake gasket ,what intake did you use?

It's the Edelbrock D4B intake. I'm not sure what gasket was on there as they we're put on by a previous owner. I put everything back together with new one's from a 273 gasket kit.