Seat tracks help needed

the bolt doesn't interfere with the roller but actually serves as a stop to contain the roller assembly in the track. Factory used special bolts though. Early had a heafty round head. Yours had a under standard size hex head. The standard size hex head for this bolt size didn't leave space for even a thin wall socket to get there. I've seen allen socket head screws used here.
And by the way... both holes were stamped out square because the same piece is used left and right hand tracks. Opposite track has stud in opposite hole.