I agree with Gene. I think you will be pleased with the ride and handling response of the radials if you keep the inflation pressures in the 30 to 32 psi range.
That tire has more than enough load carrying capability at those lower pressures. Based on the Tire and Rim Association load and inflation tables a P205/75 R15 will carry 1598 pounds at 35 psi. The capacity is 1532 at 32 psi and only drops to 1466 at 29 psi. That is more than adequate for the weight of your car.
You also might want to look at the sidewall of the tire to see the maximum inflation pressure and load capacity for the tire.
Tire Load Inflation Reference