Hello
#1 Street Porsche with twin plug heads, Dual distributor was the 1955 356 1500 cc Carrera.
I had the luck to help an very good mechanic who works on them on regulary basis. An 10 000 km Service is around 2000 $, 20% of it where for parts. You rremove the distributors from the head renew the points and go to a distributor service to set them perfect. We swap them to a special made Bosch trigger unit but purists like to have it 100% original.
Well since then Porsche made some improvments on the maintance division.
Some cars are a bit mor friendly.
Well the 964 is a very cheap and easy to maintain car compared to an Ferrari and the Ferrari isn´t much faster only mouch faster looking and louder.
If you compare it with a Vette or an Alante. I n germany to replace the Vette digital cluster is 2000 $ while you leave 4000,- for an Alante Plasma unit. And GM Delco gives no waranty if the damn thing is dead several weeks later. Wanna know other supercar prices ? 1990 Honda CRX headlight unit 600 $, temperatursensor for instrument 50$
Or just try to change both batteries from an GMC Diesel Van.
If you would like to give your german an try then follow that:
http://home.germany.net/101-232905/kaufb6.htm
Grüsse