That's 1/8th pipe thread not a regular bolt thread, so get pipe plugs and use some Teflon tape on it so it will seal. Glad to hear it's running well, did you get the brake lights sorted yet?
Yeah - I was an idiot and broke the switch off, then trapped it up on top of the cabin heater, still connected. :crazy:
Moss Motors has S.U. tools and are a real good company to deal with. I have the S.U. tool kit, it has some pointers that go into the tops of the dashpots. You adjust the carburettors so that the needles point at each other and rise and drop at the same time, the carburettors are then in synch. MossMotors.com - Restoration Parts And Accessories For British Cars