question bolt pattern

The bolt pattern on the A body cars was 4 inch, from when Ma Mopar invented them, until 1972.
Doesn't matter wether the car is drum brake, or disc brake.
So if you have the factory, 4 piston, Kelsey Hayes disc brakes on it, then it's the small, 4 inch bolt pattern.
If the car was converted over to a single piston brake caliper system, then it's 4 1/2 inch bolt pattern.