new guy with two flathead questions, if I'm allowed

[danny1940]

I newly registered to this forum but have lurked for many years. My name is Dan. I read the sticky about the purpose of the Barn, still a little confused but I think my questions are more appropriayely answered here than on the HAMB. I have a 1940 Ford tudor. Built it about 12 years ago, stock body. I run an 8BA with a merc crank, dual 94's, mallory, Max1, offy425 heads and a bunch of other stuff done to keep my flathead reliable and driveable. I had some head gasket seepage so I pulled the head. For the longest time I have experienced what sounded like light pinging in the higher RPM's. Timing, etc., have been checked many times and are in spec. The head, plugs, pistons don't show any signs of pinging or detonation for that matter. I have a set of Mercury heads. Can anyone comment as to whether or not I will notice any real difference in performance if I swap out the aluminum heads and use the Mercs? Also I use NGK B6-l plugs. These plugs don't reach the bottom of the threads in the head.Just found out when i pulled the head. If I stay with the OFFY heads can someone recommend a plug with the right reach? I experienced this pinging type sound with other plugs as well but don't know if these had reach issues as well. I'm leaning toward the Merc heads so any advise is appreciated. My 8BA for the most part has ran great. Thanks, Dan