i dont see a 9in slick for a 15x8 in wheel and i think i will go 15x8 for the track because of the lighter wheel and 15x10 for the street for lower RPM with the 4.10 gears
A wider wheel will not lower your RPM. A 275/60R15 looks pretty silly on a 10 inch rim. A 10.5 slick will work on a ten inch fine. The difference in weight between the two wheels is in ounces=not much difference. IMHO your car is a street/strip car and I would buy one tire and wheel set up. A 275 drag radial is more than enough and if you cant get an 11 second car to hook on it then something is wrong with the car.