I have bad bolt on bench seat mount, does anyone sell matching bolts? Or do I have to find a seat track? thanks to all for the help

Look here:
Bolt
about half way down the page : 0998196 BOLT BATTERY TREMINAL/ SEAT TRACK

I'm guessing, but this one ? if so how long do you need it to be ?
AFAIK, this is the only one avail ,,,,and I 'think' it's to short if you use in the phenolic spacers under the seat adjuster track assy.

Specs are - 5/16-18 x 1+7/16" length with a 1/2" Square Head

I always seem to run into seat tracks that are missing one bolt. I just use a regular nut and bolt in its place.

However, You won't be able to just tighten the nut from underneath the car unless you back it up with a wrench at the seat track.

Here's a '70 b-body bucket seat bolt w/a round head. 1-7/8" lg.

square hole looks to be 11/32" (~0.35")

...You could use a correct size/length carriage bolt...If you're real picky you could grind the convex head flatter to match the other 3...