408 stroker header size

I'd suggest the 1 5/8"-1 3/4" stepped because it's a dual purpose car and you have street-type gears and converter. Straight 1 5/8" anything will be a restriction. 1 7/8" if you go to mainly strip with more gear & converter. The stepped header can handle a lot. I've been 11.14 117+ with my race only 360 Dart @ 3540 lbs with the 1 5/8"- 1 3/4" step TTI, X pipe & straight through mufflers.