I have used Hedman 35270 headers in several 1st gens, street and strip. They are the uncoated version. These have very short collectors. So, I used collector extensions on all our drag cars. They have 1 3/4" tubes. Never had any complaints with them, at all.
Only clearance problems I ran across was when the car had a straight pittman arm. I think the V8 cars had curved arms. So, I assume that all the straight six cars came with a straight arm. Not sure tho. I'm sure there are lots of 1st gen experts here that know for sure.
I've read that the '69 arms had a hole on both ends, and are not made today. Again, I'm sure some of these guys know. I never built a '69, because of the flat top rear fender well. I liked the '67-'68 round wheel opening, which allow the tires to stick out, without rubbing. I suppose this was/is a low-budget deal. Those with plenty to spend use to run a narrowed rear end with big wheel tubs, so that they could run big fat tires, inside the body lines. I always had to go the low-budget route.
