[Alan Roehrich]

You might get by with a 3/8" x 0.125" wall. Consider a dual taper, Trend has a dual taper 3/8" - 7/16" pushrod, it's 3/8" on the ends, and 7/16" in the middle. Trend will measure for you to see if they can make something work.

You do not have to run a single spring any more. They opened the spring rule up.

Not sure what you mean about the headers. If your headers are 33-34" long, with a 16" long collector, that's about what I was suggesting, length wise. A merge collector will fit where a plain collector will.