My engine is a 1904 built with CB Performance parts, dual baby Webers and Flamethrower II ignition parts and wires. The engine and heads were assembled by a guy whose well known in the Porsche world for doing heads for race cars and Harleys and my valves are bigger, so I don't know if this applies to your engine. But, anyway, he has me set my plug gap at .030 and the car runs great. ( sorry, but the build sheet and specs are 1500 miles away)
I do my major maintenance in the spring, so the car is on jack stands with the wheels off for easy access to everything. I have installed a 4" removable access cover opposite the 1 and 3 spark plugs ( front, back, whatever, Yoda and Danny) and I can actually see the plugs. With a long extension and a ground down socket I can get to those buggers with ease through the wheel well.
I'm not as flexible as I used to be so this works for me. Best of luck.