Hemikiller, NPD also sell Retro Belt by name and "other" which are probably Seatbelt Solutions as you say. When I got mine, I thought I was buying from WescoPerformance in Ca, but they turned out to be just a distributor for S/S. What gets me is, looking at all of them, they all look the same, same parts, buckles etc., so who does actually make them? I suspect now, they all buy the same components and just add the webbing to make their own version of the same thing.
I don't understand why the need to re-install the old retractor boots. I had no problems with that. Besides, one of my old ones is broken and not repairable.
I did NOT get a boot for the sash and you're right, the inner belt sleeve is nowhere near a fit for our cars, that's why I bought the 6" cover from Seatbelt Planet and that seems to work ok, but not perfect. As for the drop sash, if you look back at my ugly pic, you can see exactly where it sits. For me it's much better than before.
For others considering buying 3 point belts, make SURE you buy with the LONG "C" bar if you're retro-fitting. None of these conversion type sets are perfect, not even the ones that are supposed to be for "our" car years. Do your research!!!! Ask questions.