I have a 2002 Silverado 1500 383 stroker and was wondering how wide I can go with tires just in the rear. The suspension is pretty stock.

 

Depends on offset of the wheel boss. I'd go x10s just to be safe

 

PD,

Understand, that there may be some additional restrictions, beyond just having the room to fit rather large tires/rims back there.

IF you have 4WD or ABS or AWD, you MUST maintain the same "diameter" tire, as are on the front of your vehicle.
(all 4 tires must be the same "diameter")

The "Tire Diameter" has nothing to do with the Rim Size, Profile or Width of the Tire.

Check the size of your front tires, then do a lookup on their diameter, and select Tires for the rear, which are within 0.5" of the front tires diameter.

The new tires could be TWO feet wide if you want, have any profile available, and any Rim Size which will fit, as long as they are the same diameter !

PS if I may add this very important comment...
After you've decided which Tire you want to use, make sure that the Width of the Rim, is the same as the Width of the Tire Tread. Having the Sidewalls operate Vertically, is critical for the best control of your Vehicle.