I am putting stock seats back in the car with stock rails. I have the hardware for the seats and rails but I dont have the seat belt bolt that attaches the rail to the body of the car. Being the importance of that bolt I thought I would check to see if anyone knows the size off hand so I can go purchase one.

 

I think it's similar to the bolts that hold the seat in, like an M12 or so. See if one of those would thread in.

You want to make sure you're using a proper high-grade bolt, that is something you don't want to shear!

Dale

 

That back bolt seems to be bigger, the seat bolts dont grab or thread right. 100% not cheaping out on those bolts.

 

The four in the square pattern for the rails, under the seat, are M10 x 1.25 thread, 22mm long under the bolt head.
The fifth (on the round rail slider under the belt buckle, at the rear of the seat) is M12 x 1.25 thread, 26mm long under the bolt head.
The belt to floor body (off of the seat, alongside the door) is M12 x 1.25, 22mm long.