I've done brake jobs for many years.

What's the deal with the 9" drums on this '70 'A' body?
There are two slots to get the Brake spoon in yet the adjuster ends up directly between the two.
Secondly I had to force the Drum off because there is no way to get anything in the slot and release the self adjust so you can spin the star to loosen the Shoes. Do you guy drill into the Drum so you can release the adjuster?

You are going to have to use a couple of screwdrivers and go at things from an angle. Happens all the time and that's why there are two slots.

I wouldn't drill the drum. I have a brake spoon with a slight offset on the end that I have used in tight access holes. I've had mine for years but I'm sure someone still sells them. I have also used a small screwdriver to push back on the plate to release the star wheel.

Take a long thin cheap(cheap ones are easier to bend) screwdriver & bend it slightly at the right spot along it's length so it will go under the barrel of the adjuster & slightly up to contact/push back the flat piece then as said angle your spoon in from the other slot to lever the threads. The left (pass) side should have left hand threads and they are easy to spot w their wierd twist on the threads so w several seconds of visualizing you can figure which way to turn the star.