Which spark plugs

[Black VXR]

Dear All, Does anyone have a book or a guide or even better, experiance of which spark plugs work best in a 1917 Stutz Bearcat please? My car has the T head 4 Cylinder Wisconsin 390 ci engine and a Bosch Dual mag ignition system.
I have champion W18 plugs in the car at the moment from the Green Spark Plug Comany.
Thanks

[lowdrag]

I've no personal experience, but a friend restoring a 1915 car told me these people were very helpful:-

http://www.spark-plugs.co.uk/