Ford over did the ports on the 351C 4 barrel heads, they needed help on the exhaust flow by closing the up, I will really be surprised if closing up the SB Mopar heads helps them flow better
This thread intrigued me , so I got to looking.
MPG head service still makes those plates , but I could not find any other brand that uses them besides Ford.
Their cam grinding arm , Cam Research showed a flat tappet cam device that breaks in the cam on the bench that had me very interested.
It is done in an oil bath and the spring pressure is ramped up as the process goes on................as they like to say in engineering , " it works on paper ".
60.00 to break in your cam and lifters seems like a bargain in time savings alone , but I suspect that it is brand specific as they only offered the service for Ford cams..