The bumps and grooves would be formed by the gasket being compressed at installation, when new the gasket would be flat.

My WAG internet diagnoses, I'd suspect that the leak you describe is the actual cause of the scored piston. It may leak fuel when off, but when the engine is running and that area is under vacuum, it'll be pulling in air from that same area and leaning out the air/fuel ratio. You can test this by spraying the area with carb cleaner or WD40 or even water while running. If the engine changes tone or idle raises or lowers, that's strongly suspect. Make sure you're not getting any carb cleaner or WD40 in the intake of the engine while this is happening, as that'll fowl the results. The gasket you removed looks fine on the visible side. I'd closely inspect the mating surfaces on the carb and the engine, make sure they're very very clean, and then double check that the carb is mounting securely and compressing the new gasket. If there's still a fuel leak, I'd check the carb gaskets and diaphragms and such. Complete carb rebuild kits are available on Amazon for $8 or so.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap