If you think you have problems now and your switching to e-heads in the spring.... Your going to love installing your new ones on the drivers side!!!!!
What brand did you buy and what size pipe/collector?
If you already have them and they are the hedmans1 7/8" 3 1/2" made for a 69 firebird, I'd seriously think about sending them back and getting a custom set made or talk to Scott Esterle at Summit.
Apparently he has had Hedman make custom 1 3/4" with 3" collectors that will fit a 74 ventura (GTO) for some of their customers but I don't know how good they fit.
I'll inform you NOW that you will Bitch, Cuss, Moan, and Bitch again and again if you have the Hedmans for a Fbird. They WILL hit the motor mount (modify the mount), They WILL hit the starter, and they WILL hit your gear box and your steering knuckle, thats with manual steering. If you have power steering
I wish I would have had a set made, it would have been well worth the extra cost for them for the time I spent making the ones I had fit. I was not impressed at all with the workmanship of the bends of the Hedmans. Thank God I didn't spend the money to get them coated! Now the passenger wasn't so bad, it's a 2 piece design on the set I have and takes a little finagaling to get them together.