Front drum to disk brakes conversion.

FYI
What you got from him is disc brake parts from the 65-72 A body line of cars.
Known as the 4 piston Kelsey Hayes disc brakes.

All that can be used on your 74, but you will have to use, rebuild, everything that you got.
You will have to use the upper control arms, and lower ball joints, that were given to you, as the existing parts on your 74 are different.
The 73, 76 cars use a different lower ball joint, and upper ball joint, commonly known as the big ball joint in the upper control arms.

62-72 A body cars use a Small ball joint.

It easily can be done, changing over your Drum brakes, on your 6 cylinder A body car.

Oh.
Look on Rock Auto for caliper rebuilding parts.