The Global West and Hotchkis arms require B-Body spindles.
If you want to use stock spindles, you'll need to check out the UBMachine or the Pole Position arms. Do a search, they've been discussed a ton, and part numbers are all over the place.
Check the threads on the Monte SS site. They are working with tubular arms to fit the stock spindle, the stock spindle with taller balls joints, and to fit the taller spindle for the 12" brakes.
They are also working with a set of adjustable arms which allow you to move the top location of the spindle without using shims.
They are pre 81. I bought them with the Hotchkis tubular upper's. Put them on, drove the car to storage for the winter, then when it came out I put the new Baer spindles/brakes on. So they work on the GN, and are in great condition, just not big enough for my brake's after being used to the STi's Brembo's.
The Hotchkis brake package includes 1101 Tubular A-Arms, upper ball joints, 70-76 F-body spindles, brake lines, rotors, calipers and brake pads. Note: Spindles will lower vehicle 3/4" and widen track width 3/8" per side. Without a-arms. $200 plus shipping.