I noticed what I think is a mold number or something on my head from a 88 N/A. Its a number 9. The redone head I am looking at has a 10. Are these revisions or N/A vs T heads. I was under the impression the only difference was the cams.
I've flow benched both designs. The "big port" flows 10+ cfm more in the upper lift area .400 and higher. At that point it jumped way out on the other design. To take advantage of that you need a cam with a 11.8-12.5mm (about .400 and higher) lift. Our cams at best are .300-.350 stock and regrinds. There are larger lift cams but they come with a large price tag.
there are probably different numbers for each design... i work in casting and i know that some of the same parts have up to 5 different molds... all identical except for a number.. that way they can re-coat or repair them while still running some.. i dont know if honda motor mounts are the same as a toyota head but its possible.