This tap should work for my 5/73 1F, right?Thought I’d mention this.
With my head still in the shop and cleaning up the block, I recently chased the threads in the block with “THIS TAP”. The tap spun in easily quite a way with little to no resistance. Then for another 3 or maybe 4 turns, I had drag that felt like I was cleaning out existing threads that were there but had not been used. They felt crusty & corroded up. So, I’m thinking that on my F.5 anyway, that I have some wiggle room if my head gets a little machining. I’ll have to do some measuring when I get the head back to be sure.