As posted elsewhere...
You could start out at 36 or so HOT AFTER PROPER WARM UP and go from there. Please remember that tire pressure increases approximately 1 psi per 10 degrees F increase. It also depends on the suspension, road temps, road condition, tire compound, etc. There are variables and there is no substitute for driving the car near limits to tune the pressure front and rear accordingly. If you are looking for a "set and forget", then perhaps 33 psi at ambient temps of 72 F when the tires are cold.
Of course this is just my opinion. Usually tune the air pressure by "feel" and take readings accordingly. ALSO, get a GOOD pressure gauge and NEVER use air filling at gas stations as they usually have water in their system (bad).
Hope this helps.