Thanks everyone for the pointers and suggestions. It's going to be fun... Spent the last two days getting stuck in. Mileage is definitely genuine, it almost looks like a steam clean would sort it out! Managed to get the engine to turn on the key... spark plugs look new (!) and have started to dismantle the fuel system...powder in the petrol tank! Cheers Grant
Another great site is: https://www.pelicanparts.com/Porsche/index-SC.htm their bulletin board has been a great help on my 10+ year restoration journey. Their prices are fair, the shipping is fast and the quality is great. Don't underestimate how much stock Porsche themselves still carry for these.
