Had the car since 1989, 'finished it in 2001' fitted the headliner today.
I have been putting the job off for some time - could not find anywhere that sold standard headliners and was worried about fitting it around the roll cage.
I found a supplier in UK - Newton Commercial that sold the 1 piece vinyl headliner. Essentially a single rectangle of vinyl with a thick cardboard strip stitched to the entire edge with 4 bow hoops stitched in.
http://www.newtoncomm.co.uk/cars/vw-beetle/model-110/roof-accessories/3448-products-3448/You need original steel bows (4) - I did not have these so bought 4 lengths of 4mm stainless rod - all 1200mm - 3 cut to 1150 and the front one 1125mm.
Fitted some dynamat along the central strip so the bows did not rattle, hung the liner up on the rods, started at the back and worked forwards.
Left the fan heater in the car for an hour - everything was very hot - and 'popped' the front strip in.
Very pleased with the final result - hopefully a bit quieter now too...
just wanted to share - if anyone wants details on supplier or rods let me know -