Just a thought...instead of drilling them out now for studs (which is fine in itself of course IMO), if the threads in them are 1/2" already..why not just use screw in studs from the rear like the style used on rear axles and commonly sold? Might save a step and some time at least...
There are plenty of different brands out there, but those as an example at least.
Some of the threads have partial stripping out, I'm a little afraid there might not be enough thread to grab them, maybe if I used some Loctite
69.5 A12 Bee, first purchased in 1976, car 169 on registry
69 Coronet R/T 440/4 spd
69 Coronet 500 Conv H code 383 4bbl/auto
37 Plymouth PU
Find your spot on earth and ride it.
Might save a step and some time at least...