Hello Nick,
I used a long open-end wrench to slide up into the b pillar. I attached a nylock nut along with the supplied fender washer to the wrench using rear window installation glue/putty that I had a roll of in my toolbox since I don't know when. It's really sticky but I was able to pull the wrench down off from the nut once I had I tightened up. I also used a drill bit stop attached to the bit so as not to go in to far and dimple the outer body panel. I believe the manufacturer was Beam and it is the retractable style with the aviation buckles. I attached the retractor directly to the floor in the corner. It seems to work well. I did not purchase the kit. I came with the truck when I purchased it. It takes a little patience's but once you get the nut started on the bolt your home free. Good luck.


Jeff
1964 Chevrolet K10 Fleetside
"A Kid's First Truck"
Follow in the DITY
1951 Chevrolet 3100
Follow his build in the Project Journals
1969 Chevrolet Camaro Convertible | 2020 Chevrolet Silverado | 3500 Duramax | 2021 GMC Sierra Denali
USAF Veteran 1983-1987 | PSP retired 1990- 2012