Headers for my 71 Demon 340.

Doug’s or tti. That’s it. If you go the 1 size fits all your rolling the dice on fit. I have had great luck, I have had horrible luck. I believe there is no quality control or actual care with the 1 size fits all nightmare headers.
This doesn't help me, if I'm getting them shipped here to Aust. I'd be really pissed off if they don't fit once they got here. It's not like I can return them, especially if it's costing me close to $1,000 aus landed. How do I avoid this?
Was looking at D543 Doug's long tube ceramic headers, they look cool.