quick question

Are the 2nd and 4th generation upper and lower A arms interchangeable with our 3rd gen?

no. neither will fit but 70 trough i think its 76 camaro upper and lower a arms will fit

The 2nd gen. F-body ('70 - '81 Camaro/Firebird) and 4th gen. X-body ('75 - '79 Chevy Nova and Nova clones such as the same year Pontiac Ventura, Buick Apollo, Olds Omega) subframes and suspension are all very similar. There were minor differences between years, though. Some years ago, I had a '78 Camaro and I worked a deal with a guy who had a low mileage wrecked '81 Z-28. Bought the upper and lower control arms with springs, brakes and spindles and the complete steering gear, including steering box, centerlink, tie rods and idler arm. It all bolted into my '78 just fine. I believe you will be OK, but its best to keep all the parts you install from the same year donor car to avoid running into one of those 'minor differences' between years.

FWIW...... Chevrolet generally fitted the Z-28 Camaro with slightly stiffer springing than did Pontiac with their Trans Am Firebird. The Pontiac engineers had a different philosophy and opted to use softer springing along with thicker anti-sway bars than did Chevrolet. There wasn't much in the way of aftermarket suspension upgrades available for those cars in the early to mid-'80s. So we used to upgrade our plain vanilla '70 - '81 Camaros and '75 - '79 Novas of the era with Z-28 springing and the thicker Trans Am anti-sway bars along with the best shocks and 60 series radial tires we could afford. Bilstein's were way out of my price range, so I used Koni's and they seemed to work very well.

It is my understanding that the '75 - '79 Cadillac Seville used revised 2nd gen. F-body underpinnings as well along with a longer wheelbase body, but I am not sure about parts interchange because I never tried to swap any of the Seville chassis components onto my cars. The Seville was quite pricey and the supply of them in wrecking yards was very limited back then. The early Sevilles used the Chevy 5 on 4-3/4" wheel pattern with 7/16" wheel mounting studs, but later year models had the 5 on 5" 'big car'/pickup wheel pattern with the stronger 1/2" studs. Can't remember just when the changeover was made. Probably around '77 or '78.

Hope this helps,

Harry