Most posts concerning the bucket seat conversion say to use the inner hole in floor plan. Well my bench seat car only has four holes total (2 in back 2 in front). I have a 72 that I'm converting to buckets and the bench seat was only held down in the back with 1 bolt on each side. After I took the seats out there wasn't another threaded hole to use. See picture. What's up with that? I temproarily monted the passenger side seat and it appears that there will be enough clearance for the retracts but barely. Any ideas why there would be only on threaded hole? THanks.

Here is a pic.

I would look under the car in the floor pan brace to get the necessary inner bolt mount location. You may even find the jamb nut secured to the brace as well. JN

Here is a picture of the underneath passenger side. As you can see there really isn't anyplace for another nut on the brace. The brace curves back toward the front and that would not be inline with where it should be. How is it that this car only has one on each side? Was it stock this way? From what I can tell it looks like the original floor pan.

There are two holes in the rear outboar leg of the bucket seat. Only one is used to bolt the seat down to the existing hole that was used by the bench seat. You have to weld in a bracket in for the front outboard mount and a long bracket for the two inboard anchors. These brackets have threaded studs. It worked for me.

I just welded in my bucket brackets last night. The inner hole (normally the rear of the bench bracket uses the inner of two existing holes an inch and a half or so apart) should line up with the outer of two holes in the bucket brackets (each outer has two rear holes). I have switched the same brackets twice, they were cannibalized from a previous Chevelle. All my Chevelles were '66 though, there could be some differences, never heard of any though.

I think the assumption that there are two threaded rear (bench seat) holes through the floorboard is inaccurate (at least on all cars). Unless my car has been modified I can't see where it would go. To get my bucket conversion bracket mounted I will use the outmost hole in the bracket which will set the seat inboard as much as possible using the ONLY threaded hole I have. The other brackets will be welded in.

hmm, thats very interesting. Even my 69 which was a bench originally had both rear outboard holes punched in the floor with the jamb nuts in the brace. I was the one who converted it so I can attest to this. If you want I could measure the car in the garage a 67 SS coupe, which was original bucket seat car so that you can get proper placement if you wish. JN

If you want I could measure the car in the garage a 67 SS coupe, which was original bucket seat car so that you can get proper placement if you wish. JN

I have some measurements that someone emailed me showing the dimensions from the sill plate screws. Mine seems to be close to the drawing. If you have time maybe it would help to measure from the edge of the frame to the center of the hole you used. (from underneath). Thanks for the help.

I have some measurements that someone emailed me showing the dimensions from the sill plate screws. Mine seems to be close to the drawing. If you have time maybe it would help to measure from the edge of the frame to the center of the hole you used. (from underneath). Thanks for the help.
Both sides measured from the top edge of the frame rail measures 3 3/8 inches inward, and 3/4 inches from the square edge of the brace the jamb nuts are secured to. These meaurements are to the center of the bolt, and are for the inboard rear seat mount, not the welded plate next to the tunnel. JN

Mine measured 3 1/2 inches from the top edge of the frame. From your measurements, I think mine should work out fine. Thanks a bunch for the help.