Nice one Don and Craig, good to see the plan came off for you.
I wasn't sure if I was able to use the standard seatbelt mounting points on mine (not an Arntz of course) so I added a rear central mount point early in the piece. Some thick as angle, some 2 x 2 x 5/16 RHS and some 1/2" plate at the top.
The standard mounts are pieces of 40mm x 40 mm rhs welded to the side of the rails with some flat plate capping the top, the hole 7/16 is then tapped in for the bolts.
View a few ideas and I'm sure you will find what's easiest and best in your case.
Cheers
