OK, bought some brand new Mikes XS left right petcocks, 42.5mm pitch. That was the plan.
The tank uses the cups at the front end as a mounting feature, and has to rotate about these points down into position. However, these brand new petcocks crash with the frame. Playing around with them, they either crash with the frame on the rear valve cover.
Anybody want to make an offer on some brand new petcocks - reach out to me privately.
Ordered a set of these petcocks for left right, no reserve. I will still use the other petcock in the rear of the tank, which has reserve, maybe 1/3rd of a gallon, enough to get off the freeway. Made some 1/4 NPT thread bungs and welded them into the tank. They can be seen in the tank pics below.
After that, had to spend about an hour and a half cleaning out the tank, removing tiny bits of metal that were introduced in this last step. Very painful, slow work. They wouldn't shake out, wouldn't blow out, wouldn't vacuum out. But, if I used a magnet and shaked the bits until they hit the magnet...
Some shots of the finished tank. 10.17lbs. (Still needs sealing and of course new paint.)
I had to relocate the coil, to make more capacity for fuel. Spent the day today making a new bracket for that.
Here are some quick start - finish pics.