I can tell you that Hedman Husler Hedders hug the floorpan well--they tuck up even with the bottom of the subframe. Hookers do, too, but both are expensive. My '68 sits low all around with a forward rake, and I've scraped my headers on more speed bumps than I care to recall lol. It's just the curse (or great power advantage) of headers. You live with it and take speed bumps crossways (chuckle.) My car has never bottomed out at speed, though. You may have some weak springs. Good luck!