Read pumaracing artical on CVH head... it says that 81SM6090 casting would be fine for big valves, but also it says that there are two tipes...
"The cross-hatch casting has a ribbed cross-hatch pattern on the external sides and has thicker port walls and a better port shape. Only the cross-hatch casting can be used for 45mm valves."

Anyone got a picture or could explain this in other words?

I have 81SM6090 from 86'XR3 and D85SM6090 from 88'RST (the one isn't even mentioned in pumaracing)