Is there a difference between 71 and 74 disc brake components? looking to convert

There is a difference. The early disk brakes where a 4 piston caliper small bolt pattern on the wheels.

The later 73 and later disk is a single piston caliper large bolt pattern on the wheels.

The later 73+ is a popular upgrade as it gives the big bolt pattern for wheels. In addition the ball joints and just about every other part is also cheaper for the 73 and later A body cars.

To do the swap you would need upper a arms with ball joints, spindles, lower ball joints, rotors, calipers, brake pads, and probably new brake lines.