Dan, not neccessarily your fault, but you stepped into a trap. These heads and P/C were evidently purpose mated long ago, likely to save the over cut head chamber volumes (yet to be determined), and the custom work, known only to the machinist and the owner then. In truth, the correct use, and suitability of these pieces, to work with each other, is the responsibility of any assembler, and that, may well be the takeaway in this tale. This prior mishmash of various parts, is why my recent S90 build, has taken the betfer part of 2 years, and many hours of research. If it was easy, anyone could do this stuff. Like others here, I laud this thread, and it's teaching value to all. As these cars, and engines age, this issue will become more of a challenge.
You have received great advice here, from some of the most experienced, and current "in the know" folks, who base their council, on fact. We wish you the best of luck, going forward, and that car, from the photo, appears to be well worth the effort.