phillb wrote:
The vinyl they used for the dash in the Mk 1 is the same as the rest of the interior vinyl, see pic. Perhaps if you keep an eye out for some old black interior vinyl (or another color and dye it)
Unfortunately you need quite a big piece. Maybe part of a old rear seat. Remember other cars from same era may have the same vinyl.

If you have the right material, use it.
I know this is probably a slightly "picky" point but I have the impression that the thickness of the vinyl used by the factory for seats was thicker that the covering for other areas like f/r dash/parcel shelf, f/r side pocket liners, rear wheel arch covers etc. At the time the factory had the luxury of ordering the same texture pattern in various thicknesses. Most vinyl sources now provide seat cover thickness only and we have to make do.
I've just fitted a Newton Commercial vinyl to the dash rail. It looks nice. It may cause clacking tongues at shows…. I could have used a local material for a lot less - in the end the car will drive just as well.
Bill