Hi swartie - the gas a just shock were as below:
(AC513KG5530) 565mm / 345mm - rear only
Go to this page and it tells you all about it....
http://www.vwheritage.com/ssp/Shock-Absorbers/?templateID=ssp
To accurately measure the shocks your meant to remove the shock and measure the difference between the shock bolts when the van is back on the ground with the wheel on....however I just measured them with the shock on....seems to have worked for me.
The shocks have made a massive difference - much better ride and no banging. I did have the ball joints done at the same time though.