I have a set on a 75 duster.....and I have a set in that is in a machine shop being ported....actually one set of SM and one set of Eddy....both getting 2.055 valves ...same shop...same flow bench...same guy porting them.....
Let us know how they turn out. Your machinist will be a good judge of them. He has probably seen hundreds of heads and knows which ones are good and which ones are better.