leaking...f...king valve covers ???

Yes this too^
Which may show up as a weak imprint in the gasket (which you can see when you take the vc back off and look at gasket. The imprint will be zero to very shallow if it's not compressing (at that spot).
Are you able to achieve full torque when tightening these bolts?
If yes, as Bruce said, bolts may be bottoming. Try a shorter bolt or add washer(s). A feeler gauge beneath bolt flange may help. That would be a hell of a gap though.
If no, address threads.
Run a straight edge along head rail.
Run a straight edge along vc cover flange. The gasket should fill a small gap, but you'll notice a large one. Least likely.
I had to grind the vc cover so deep at some spots to clear intake runners that I'm past the flange on the vc, and I'm still sealed. I siliconed OUTSIDE the vc after installation at the gaps around intake runners.
This is on small block with rpm air gap mani and cast Vc's with cork felpro's.