Call Mike at MRL he uses them quite a bit on his builds , he might disagree with your assessment on their quality tho since he has been known to make around 600hp with them .
They should be back in stock soon. Maybe by the end of this week we were told. We build them from bare castings. We change out the guides(total garbage), put in good SS valves, and do a 5 angle HP valve jib that we have tweaked over the years. We put in the right spring for your cam, not some Chinese generic pos that is no good for nothing. With a stage 2 port clean up, our PC SBM heads will make over 500HP. With stage 3-4, they have been over 600+HP.