I "misplaced" my seat rail mount nut for the stud that comes up from the floor. I've tried hardware and automotive stores but now one had it. Does anyone know of a link or at least a size to help me find one? Thanks.

 

Use an M8 x 1.25 pitch Metric bolt, about 1 1/2" or 2" or 40 to 50 lenght, will screw right down into the floor nut.

 

You misunderstood, I need the Nut that goes on the stud which comes up through the floor. I should also of mentioned it's 1996 xj

 

Any salvage yards nearby?

It's going to be a metric nut. Did you check for metric nut assortments, or get several different ones to get one to fit?