I've been running the 17 x 9" ZR1 style wheels (Camaro SS wheels) w/ 2" adapters for about 2 years on my '69. I check the torque of the spacers about each 6 mos and never found anything loose. I have run the car at auto-crosses.
I had to use a short 255/40-17 tire on the front 17 x 9 wheel to get clearance. I have a stock 2" lowered supsension, except for Heidt upper control arms and Guldstrand mod. It is very close, I had to grind the rear bolts that connect the inner fender to the outer fender to get clearance in turns. Each car is different, so one must measure carefully.
Gary M.<br />'69 Camaro<br />Red Pro-touring<br />383 ci 440 hp