The belts I have are from Seatbelt Solutions via Wesco (just a distributor). I ordered them with an 8" drop sash and star burst buckle. Looking at other manufacturers, Seatbelt Planet for example, they all seem to use much of the same hardware, i.e. they all look the same.
For me being a shorter guy and therefore need the seat more forward than most, I found the tunnel belt portion to be short compared to the original. Also the hard plastic sleeve used, seems to be pretty much a generic piece used on many different cars. It does not fit ours the way it ought to. What I did was to order separate sleeves from S/P (they sell accessories separately) and cut them to what I wanted. Still not perfect, but better.
The drop sash, could also be better and come with a cover for looks. I tried a sleeve, but it looked worse, so I took it off.
My biggest complaint is the buckle tang piece, which is basically fixed after adjusting for personal fit, stops the belt from fully retracting which leaves a loop of belt hanging. Finding the belt is awkward at times and then I find mine locks unnecessarily when trying to buckle up. Very annoying!
Why these manufactures still continue to use this sort of buckle tang and not the free sliding type we all have on our daily drivers, is beyond me. Afterall these are NOT meant to represent the originals, but a safer alternative.
Here are a few pics of mine. 1750, 1708,1714 are what I didn't finally use. Pics loaded not in order.
EDIT: another thought might be to look around the "auto recyclers" for suitable belts with the free sliding buckle and fit the tunnel buckle you already have. Now, that's a thought!