I did not realize until looking just now that one could buy NPT helicoils.
https://www.mcmaster.com/product/91733A401If this was to work, I suspect you’d have to use some sort of fuel resistant epoxy or sealant and make the (1/8 MNPT x 5/16 female inv flare” fitting a permanent part is the carb.
The investment even in that scaled-down project would far outweigh the replacement value of a Rochester B.
I am not terribly familiar with the types of epoxy’s that folks use to plug fuel tank holes and what not. You could probably go even more cave man and just drill a little oversize, goop up your fitting of choice, and jam it in there.