Ferg,
What we did in our 88 Westy which has the narrower rear seat than the standard Vanagon, was to add an extra belt for the middle using the same mount points with a bit longer bolt to accommodate 2 seatbelt end plats' thickness. The same should work on a 914.
So unless you're trying to stay all original, I'd suggest you get a lap belt that will fit & with the angled plate or bend one to match, or use flat if not an issue. IIRC the 2+1 seating option wasn't offered after 72 MY, & only outside of the US; or it may have only been 70-71 MYs with the fixed pass. seat - I'm not sure.
However, the center position seating is really tough with a center console, which is why my PO/OO had removed the Center Console before I bought my early 73 2L in 12/75, in order to seat their 2 kids for ferrying around in the 914 (3rd kid on the way was why they sold).
BTW - some of the early 73 MY production bodies from Aug. or so 72 still had the extra mount point in the floor. Yours may since IIRC it's an early VIN. So I agree with Andy to wait, then see what you have & go from there.
IIRC, that early 914 optional center belt was like the non-retracting rear seatbelts used in 1960's & early 70's Bugs, Ghias, Buses, 411s/412s, etc., so that may be an alternative source for used, NOS, new repro &/or reconditioned ones that would be close to or same as OE.
Maybe post some pix on here as a guide to how you do it, if you do, for others to see if they want to tackle it.
I may even do it if I have the extra mounts in my 8/72 built 73 2L!
Good Luck!
Tom
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