The braking system adjustment you describe is the same as mid 50's Chrysler products.

Each brake shoe has an anchor pivot on one end and the wheel cylinder on the other. The adjusters center the shoe vertically for proper concentric contact with the drum. The adjuster also moves the anchored portion of the shoe outward for the brake adjustment we are typically accustomed to.

Given the shoes can be adjusted for proper concentric contact, the need to arc a shoe is reduced but might be of some benefit.

A firm ish and long peddle travel is usually due to swelling brake hoses / too small a master cylinder bore diameter / too large a wheel cylinder diameter / brake drum flex / backing plate flex / brake master push rod too short.

Not getting much braking effectivness may be from the shoes not making full contact with the drum. Do the shoes show wear along their entire face? ( not having wear in the last 1/2" top / bottom isn't an issue. )

Do you know what the bore sizes should be?

Does this car still have a single circuit master cylinder? While not related to the braking issue, I'd be putting a dual circuit master cylinder on this car for safety.