Posted for your comments and critique: the 3 point seat belts that I finally finished installing in the 68 convertible.
Front seat belt reel bolt is a 4" long 1/2" diameter Gr5 bolt that passes through the piston cover, the metal behind the piston cover, and then through the inside metal of the car. (good thing I know the names for all these things, eh?) I also swapped out the original 6 piston cover bolts for Gr 5's as well. With the reel anchored in this location, it's all hidden by the arm rest, and the belt comes up through the gap between the arm rest and the side of the car. [see pic1 below] The belt reel sticks out just a bit too far for the arm rest to fit in place as it normally would, so I had to "shape" it around a bit.
Back seat belt reel is the 7/16" Gr5 that came with the kit. I wasn't satisfied with the sheet metal that it bolted to in the trunk, so I added a 3/16" thick, 2 1/2" wide strip of steel that bolts to an existing hole in the trunk hinge. [see pic2 below] I don't think it's gonna move.
I think they look good, and they feel quite good. [Pics 3 & 4] With all the windows and top down, the front seat belts do vibrate a bit in the wind when you get up to speed, but that's okay. Best of all, I feel better / safer about taking the boys for a ride. [Pic 5]
Lastly, I'll likely be selling my 5 complete original belts (ebay?) to help finance the project. Not sure what they're worth though.