Hi mrboj, they look pretty sought into ...😳 I don't know if it's an option but have you thought about cleaning them up and building the corroded area with mig weld then grinding back to shape.....I have done that in other applications ( not on a cylinder head bolt) and it worked ok....but I guess it also depends on if they are just mild steel bolts....I know some head bolts are " stretch" bolts and are one use only, can't see these been the case. A bit of work involved granted but not that out of the way. And the other more logical option would be a reputable engineering firm they would knock them up no bother...I would be interested in how you got on as I've got head gasket to do on my bis when weather picks up and could very well face the same problem as you, I'll find out when it pull it apart...good luck with it tho....look forward to seeing how you've got on....NJ