Way to go Pascal.

Thanks guys ! What's weird is that 75 has a 4 barrel YT 400 with 5C heads and single exhaust, no AC or power Windows/door locks, also a posi, some buyer wants different options for their cars I guess ??? The seller is keeping the 400, trany and posi diff off the 74 and seats, too bad... the cars are 2 hrs away from my place, it would be too costly to make two trips for these cars...

Pascal your are right on 74 and earlier models. Once Catayltic converters appeared in 1975 on all GM's dual exhaust went bye- bye (with a few exceptions)  so yes a 400 4bbl single exhaust would be factory for 1975 on a Grand Am.

On a 1974 the single exhaust would be found on the standard Grand Am  engine, the 400 2bbl, of course RPO N10 - dual exhausts, was always an option on most Pontiac V8's that did not come with duals.

Hey Pascal, I just peeked at PY Forum and I see you got an identical answer from Rick, 77canamman, who is the POCI Technical Advisor on 73-77 A bodies. Big Ray knows these cars pretty well too 

I'd check the laws in MB before ripping off the converter though. I have used pieces of the 1975/76 Caprice 454 dual exhaust system in the past on '75 and up A bodies. It maintains the converter in place but provides the desired look, sound and some HP gain.

I picked up ( got it delivered from Arborg to Elie I should say ) my 1975 Grand Am yesterday and 4 of us parted out the 74 within 5 hours. I got as many parts I could salvage off it and managed to learn how to remove a windshield in the process, wasn't as hard as I thought. I took home 2 doors, a trunklid, hood, interior trims and panels, gauges, switches, cruise control, front bumper, grilles, tail lights, chrome trims, all seat belts, double hump trany crossmember, 4 honeycomb wheels, 2 rally II wheels, console/shifter, sport steering wheel, louvered side windows... The seller kept the drivetrain and the seats, we had a great day ! I was hoping for a 3.08 gear ratio in my car but it has a 2.56 like the other one had at least it's a posi diff.

Well worth the effort it seems.