screw size for a 110 fuel tankreturn plate

just bought a new 110 fuel tank but run into an issue with the 5 threaded holes that secure the diesel return plate
my old tank was m5 but not this one
i've tried 8-32 and 10-32 so they don't appear to be unified so my thought was a ba size maybe a #2
TIA

tried all my small taps unf unc unef ba and metric both std and fine non fit so i came to the conclusion that the threads were cut with very worn tooling and were under size
i ran a m5 down one and thread pitch seems correct so did all the rest ,whether they were metric or not i have good thread engagement and once i've vac'd out the tank for any swarf i didn't catch i'll be happy