Hey ykf7b0, I'm your Road Runner cousin.
Mine is a 68 RR, 505 Hemi, TTI headers and collectors, TTI 3 inch exhaust, H-pipe crossover, Dougs 3" electric cutouts, just in front of DynoMax Super Turbos, then 3 inch to the stainless tips. Works perfectly, lots of room, room for the Gear Vendors...