Mac 351w longtube headers hit floor board

I mocked up my drivetrain and found the pass side collector hitting the floor board. Driver side looks fine. When I measure the collector height from the ground, the pass side sits up 1" higher, which is causing the floor board interference. The headers are 1 3/4 Mac longtubes on a 351w with convertible mounts. I also bolted up the headers with the engine block and heads on the stand - the collectors are still uneven by the same amount. Anyone else have this issue?