I would not sweat the head gasket. I used to rebuild 273's all the time. Never would I use the steel shim gaskets and did not like the OEM composites. Theoretical BS as far as I'm concerned. If your head surface is flat, Fel-Pro's will last forever and never leak fluids or compression. I've run them on all my 273's for decades. Zero problems. You are doing great for a what you have done. Leave the last .001 of a second for the racers.
The pressure plate looks like a 10 scalloped B & B to me.
