I've had CCW and Jongbloed wheels in those sizes.
Jongbloed Racing Wheels - Contact/Service
I have run 17 and 18 CCW rims similar width with R rated tires on my 993 race car.
The 18s were just too tall and heavy, the 17s were fine.
Currently 74 RSR flares with 15x12 and 15x14 with 23.5 tall front and 25 tall rear Avon bias ply slicks.
My current Jongbloed 15 diameter rims and the bias ply slicks saved 10+lbs per wheel and tire.
Jamie Lipman's photos.
PS don't bother with the American Racer slicks, cheap slicks that start off crappy and get worse.