#3 - saddle belts, not black
Have you tried Juliano's?
http://www.julianos.com/seat_belts.html
Also, consider getting belts/material at Juliano's and then sending them off to someone to rebuild using your original retractors. I had to have my retractors rebuilt by a shop specializing in this - I hate to admit but I gave up after destroying about 3-4 sets of the little brittle clear plastic retainer tubes... I had a company named ssnayk oyl
http://www.ssnake-oyl.com/ rebuild my original retractors. So, I'm guessing they can probably do whatever you need. They weren't exactly responsive and that was a bit annoying at first, but it's a smaller business and ya gotta figure they are busy.
I understand you are wanting to add shoulder belts, but maybe this will at least give you a place to look for some answers. Factory optional shoulder belts are like hen's teeth...
And black truck with a saddle interior is a beautiful combo, would love to see a few pics of your truck, especially the interior. Good luck!