That kit is not needed. These bolt right into the existing holes without modification. Bench seat should not cause any problems. I would think it fits just fine.
I installed the 3 point seatbelts yesterday. It took me about 45 minutes to install the driver side belt including downloading the instructions from the Summit Racing website, studying Acornridgeman's photo, gathering all the tools and enlarging two holes in the new belts. The passenger side took about 10 minutes. Acornridgeman's photo was of more help than the instructions. The belts look super, function however is a different story. They can be a pain to put on from time-to-time much like the factory belts in my 1997 Mustang Cobra. If I had it to do over I would still install the new belts. I took this not-so-great photo in my cramped garage.
Nice pic of the bench seat. Thanks for posting it. I didn't need to enlarge the belt holes. What didn't fit? Also, is it just the twisting around to grab the belt and pull it forward that is difficult for you or is the comfort once buckled up bad because of the belts position? A couple passengers in my car have had a bit of trouble figuring out what strap to pull on when hooking up, but once on everyone has been very comfortable.
I needed to enlarge the anchor bolt hole on the retractor itself and the bolt hole in the strap attached to the driveshaft tunnel. All my bolts are factory original. I find when pulling the strap forward thus up from the retractor it tends to get hung up from time-to-time in the attachment anchored to the roof. My `97 Mustang Cobra's belts do the same thing. Once the belts are on, they are fine.
