I think you need to determine if the problem is electrical or fuel. You first say it is losing spark, then you start discussing fuel issues. Not a big deal to tie it down to one or the other. If it is spark, simply buy one of those $ 5 spark checkers that goes between the plug and the wire and see if that is what is going on. These flatheads didn't have the hottest ignition systems to start with, being only 6 volts, and if you factor in 61 years of age they can start to have some problems.

Flathead distributors were known to have problems when conditions were moist, and also when they get warm. One guess I would have is that something in the distributor is opening up when the temp goes up. You have thrown a lot of parts at it, but I think you may have to spring for a new distributor assembly, if indeed you find your spark is going away. I think Speedway and others sell new improved distributors for these, and when I get around to building the 46 flatmotor I have I am going to use one of their units for sure.

Next time it stops running do the spark check thing and then you will know for sure what is happening.

Don