I decided to check the combustion chamber volume on cylinder #1. I repurposed an old CD case, sealed it to the head with grease, and eventually filled the combustion chamber with about 43cc of isopropyl alcohol, using the very precise measurement tool in the photo. So, it looks like the heads have not been cut down by any significant amount. I've been chatting with Dale from ModMax, it looks like their stainless intake valves don't have the deep dish and raised shoulder that the factory intake valves have, and would give me the PTV clearance i need. I'll need to lap them in the heads, but that'll be easier (and cheaper) than pulling out the pistons, driving about 300km to and from a machine shop, paying to cut the pistons and re-installing them. I hope. The factory exhaust valves have significantly more PTV clearance than the intakes, i'm not worried about them.
On another note, here's a photo of an exhaust port with the exhaust gasket opening marked with a sharpie. Bill, is there any advantage to matching the long side of the port to the gasket/header, or would that reduce exhaust velocity? ...regards, kevin