I have had 2 of those modern "no cd" units. The one I fitted to the (now sold) Hi-Top was made by "Bass Face" and was OK, but the one I recently fitted to our Ti-Top is just ACE ! - Don't let the low price put you off, it works really well, the radio pick up better than any unit I have owned, it even plays video off the SD memory cards

and has a remote control ! - link
HERE. Other models are of course available, as "they" say. The thing I like about "deckless" units is, you can buy a bunch of small memory, cheap SD cards, and use them like you used to use cassettes. As in, make "compilations", I put simple numbers on the cards, "1" = Blues, "2" = Rock, "3" = 60's, "4" = chill out, etc etc. I keep them in a small cigar tin on the dash. Oh, the only thing I don't like with it is the radio station selection is a bit of a faff when driving, but you soon get used to it.
Re wiring. As far as I know, there is no simple adapter to go from a 30 year old VW connector to a modern unit. However, it is not hard to figure out.
Your van will likely have 4 pairs of speaker wires behind the dash. Each pair will have one of the wires with a different coloured strip on it. (iirc, there are 2 pairs with brown as the main colour and a stripe, and 2 pairs with grey as the main colour with a stripe). The speaker wires from the radio also have a stripe on them. Just remember "stripe to stripe" when you connect each of the 4 pairs up. The only slight complication is finding out which wire in the dash goes to which speaker. This is easy if you get your meter out and set it to it's
lowest "Ohms" setting. Then (ok to use your fingers), temporarily touch each
pair of dash speaker wires onto the probes of the meter, as you do so, a speaker will make quiet click each time you touch the probes onto the wires, so you have identified which speaker that wire goes to

Then it is just a case of connecting to the appropriate wire on the head unit, remembering the "stripe to stripe" rule (note, it does not matter what the colour of the stripe actually is). It is OK in my opinion to use insulation tape for this job, just as long as you do it in a very neat and sensible way. Or you can use those "chock blok" connectors, though in my opinion, it is a bit harder to do a neat, proper job (no bare bits of wire showing) than with a well done tape job.
RE the other wires. You have an earth = black on the unit, brown on the van. Again, on the unit you have a red wire = main live 12 volts input and a yellow = live 12 volts input for the units "memory", connect those to your leisure battery circuits "live" terminal.
Note re connecting to your leisure battery (or main battery if you prefer, via a spare live in the dash). That unit I linked to, unusually these days, has a very very low current drain when off (I forget the exact figure) so it is OK to have both lives (red and yellow) permanently live. Those red and yellow wires can be joined at the dash end and a single wire used to connect to whichever battery you choose (I use the leisure battery). If running that wire back, under the mats, don't forget to have a fuse ("inline" fuse, 10 amp, or, I prefer to use those "fused accessory distribution boxes" you can get) very close to the battery end.
Phew, that turned into a bit of an epic
