I feel pretty confident that the A87 in the picture is open or at least a semi-open chamber, and my speculation about running on pump gas is exactly that, just speculation. Chambers would have to be CC'ed. And yes, I don't think a peanut head milled .060 would run on 87 octane...in my unprofessional opinion.
Seriously? hmm, I wish there was more info on this subject :( I have read multiple places that the late production 1973 model year 510 L18 was the first JDM EFI. And wow, 10 hp just from EFI that's impressive! Kinda hard to believe it is more than an L18 turbo though, and is this L18T a production motor? I would love to find all of this info in print somewhere, but not sure that will happen....:(