Fred,261 head gaskets aren't rare,there just seems to be a limited choice of brands and designs.
The style you mention is what was in the engine and the replacement gasket that got ruined.Why it was seeping oil on the sparkplug side of the engine is a mystery to me.The block and head were machined, they are flat as Paris Hilton's chest and again no leakage of coolant or compression.When I built my other 261, a light smear of Hylomar sealant was used on the edge of the gasket on right side, absolutely no oil seepage on that engine.
I run the 37 truck pretty hard,maybe a slight oil leak is because of this, and maybe the seepage might not bother some one else.It never leaks on the ground, just gets all over the engine ,makes a mess.