There are some things that can happen falling a foot off a jack that
merit serious consideration. I'd get it on a lift and look it over
VERY carefully paying particular attention to where the front crossmember
bolts to the chassis, also where the frame horns go from under the floor
up beside the engine. Also look over the rest of the frame.
I had a 67 122 almost rust in two below the battery box - first clue was that
the door didn't fit right sitting on all 4 wheels but when I jacked it up it
came back together.

But the other guys might be right, it could just be the exhaust.

If your tailpipe consistently drags you need to choose another route or
adjust or cut off your tailpipe to where it doesn't drag. Stresses on the
exhaust system are certainly high enough to damage ANY exhaust system if
it drags the pavement. Might want to consider a side exit. Then you can
tear up your bumper.......
--
George Downs Bartlesville, Heart of the USA!