I can give you a little info on the 17's, 'fraid I'm not as much help with the early A's as I am with the '67 up cars though. What are you running for spindle and brakes? If you're doing the 73+ mopar disks with 17's you'll be limited to about ~5.6" of backspace on a lot of rims because of outer tie rod interference. Some rims can get away with more than that (I've heard of almost 6" of backspace working on the Mustang Cobra R rims), but 5.6" would be the "safe" number where most rims would still clear the tie rod without any issues. That would also probably make a 17x8 your best bet, I don't think you'll be able to pull of a 17x9 with the fender clearance on an early A, but like I said that's not my area of expertise. I have heard of 245's being run on the front of early A's.
You might try member
@vntned, he has a lowered early Dart he runs 15x8's on with 225's. With 17's you can definitely run more backspace and I would bet based on vntned's backspace numbers a 245 would work if it was the right height, a 245/40/17 would be 24.7" tall and that should work on the early cars, I usually shoot for closer to 26" tall on the 67+ cars but I know lowered early A's can't run that tall of a tire if there's a lot of width to it. There are some good, soft compound (200 A AA) tires available in a 245/40/17.
If you haven't seen this thread there's a few folks on here that do road race stuff with the early A's, a little different than CAM-T but I bet there's still useful info there
Trans-Am info for the 1966 Barracuda
Not sure how light the car is, but I know even on the early A's a lot of the road race cars were running larger torsion bars, in the 1.12" range. And the vintage road race guys don't have anywhere near the tire options you have for CAM-T, with the soft compounds available for use in that class I think the 340 torsion bars will be undersized.
