Hi folks, I'm trying to find some info. on a National Gas Engine, made in the UK. It has a 6 1/2 x 12" bore & stroke, 43"flywheels, & a serial # in the 13000 range. This engine has a sparkplug right now, but I'm guessing it use to have hot tube ignition. Any help will be appreciated, as I'm thinking of buying this engine. Thanks, Dwight Vivas Matoaca, VA.