Tire/Wheel size on a 47-55 chevy truck

Hey... I have a 51 GMC sitting on a 84 s10 chassis and I am thinking of changing the wheels/tires to lower it a bit. Right now I have 15x8 wheels all around. the tires are 285/ 60 r15 in rear and 235 in front. Need something that will fill up the wheel wells in the rear.... thanks

 

I have a '50 chevy on an S-10 frame. I am running 14x6 and 15x8 wheels with 205-75-14 and 235-75-15 tires.Truck sits low and has a rake to it.