It depends if you want a perfect bolt on. If I recall right, 80 or newer have metric fittings in the box and possibly a different sized coupler/rag joint but otherwise will work.
I put a late 80's Trans Am WS6 box on my 64 GTO but I had to adapt the hoses to the box as well as do some mix and match of parts to make a rag joint that fit. What a killer steering box though! It was under 2.5 turns lock to lock if I recall right.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
The Camaro and Trans Am boxes will physically bolt in but they have internal stops inside the box which limit the amount of travel. They will not turn the A body steering linkage to the locks. I Have driven a 66 Beaumont with the TA box and it is annoying when trying to parallel park or do U turns. Noticeably larger steering radius.
Monte SS or Grand Prix Aero coupes have boxes that will work (if properly centered) but the Grand Cherokee box is the easiest to find and best choice. You can buy them over the counter at parts stores in the US quite reasonable.
The Lee manufacturing inserts to adapt to non-metric hoses work very well.
I have quick boxes on my 68 Acadian and 67 Chevelle rag... both Monte SS boxes.
Gary
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72 Nova SS - Minitubbed 70 Nova SS - #'s L-78 Bench Stick 68 Acadian SS clone - factory air 67 Chevelle rag - SS 427 clone
researching all those options ,Thanks guys for all the input. heading to wreckers this morning to look at a GC, 50% off this weekend, also waiting for call back on AGR box