Hi,
For my 1973.5, I am currently using 6x16 Fuchs with 205/55-16 tires. My car is lowered and it developed a rub which was corrected (Rothsport Road and Race did the work) by upgrading to turbo torsion bars and adding a bit more negative camber.
For your SWB car, I would check with some of the SWB folks to verify this will work for you as well. You may be about to get some good feedback on your plan at the Early 911S Registry BBS on this topic (
Early 911S Registry).
I see you are in in Portland! You can meet fellow Pelicans at our monthly gathering (
http://forums.pelicanparts.com/pacific-northwest-us-wa-id-ut-hi-ak/500446-oregon-pdx-beers-burgers-second-thursday-every-month.html).
There are several very good shops in PDX who can also help you figure out what you need to do. where are you located?