[Alan Roehrich]

Considering that the exhaust ports for a 409 do not have a large cross section area, I agree with Mark, 1-7/8" is as big as I'd go with the 1st diameter. Not sure I'd go as small as 1-3/4", but it might work.

I think the 4-2-1 or tri-y is probably the ticket for a stick car especially. But you need the right cam to take full advantage of them, and you have to make sure you can get the correct firing order cam for the headers you build. You might be surprised how small and exhaust lobe you can run with a 4-2-1 header, and what it will allow you to do with the intake lobe and the LSA. Considering the lift limit on the intake lobe for the 62 409, that might be a really big deal.