I've seen the lap belts and shoulder harnesses installed. I'm sure someone will step in to give you more information. As to the anchorages, it's wise to have a huge washer or metal plate around the bolt that holds the seat belt to the floor, lest a rusty part of the floor should rip out from the stress on that bolt, during an accident.

Type 'seatbelt' in search and see 7 posts. Photos of my ft. seat belts are there.
ps: Note that lap belt attaches into the seat frame so use grade 8 bolts in the threaded floor seat attachment; same in seat to adjustment rails. Be sure about 5" of belt is showing or it will be too tight. Had to redo mine; also sit in seat to determine actual location of belt at seat before attaching. Skinny or broad does make a difference.

The Beam part number was WSCH 324 I couldn't find it anywhere.
Can you describe the details of the part you installed.
Does the same part fit driver and passenger side?
Thanks,
Dean

They did change numbers, call them. They have a website.

I checked out their website. They really have a huge inventory. One of those should do the trick, I'm thinking the version with the cable short end, which would seem to be more adaptable to attachment to the seat structure,
Thank you again.

You drill holes in the seat frame under the seat at the back; remove seat bolts at slides or slides from floor and tilt seat to lean against back seat for access. But do think you need to remove seat for shoulder belt installation.

Edit: call and they will give you the new number. Thought I put it on here somewhere but I can't find it.