www.mortec.com is the link I was looking for.

I will give you an example of what I had done.

a friend gave me the engine out of his truck, I didnt know much about it so I went looking to this link and found the engine casting number was #3970010. from 69-80's the head numbers are #3998993. with 75cc chambers

but I had noticed that the 60cc chamber head numbers, and made myself a list of them and went to a few boneyards. and found a good rebuildable set for $20. each, and at that price you cant beat them.