I am not sure, I will look to see if its on the old invoice. I believe its all about installed height, but what I know is the stock type adjustable rockers that are on it currently line up great which should indicate the heads are a good copy of factory.
I know when I went to 318 valves in my ported slant 6 head, the 318 valves were some .300" longer, so I had to have Mike at B3 make some custom shims to get the geometry correct.....and it is spot on. Mike can help you if you let him.
