You "need" what ever size tire you *want*. It has nothing to do with lift height.
You choose lift height to allow for tire size...
The RC 4.5" lift, per RC, will clear 32x11.50, so some trimming and bump stopping will be required to fit 33" tires.
As for the rims it's good that you got better back spacing, but what WIDTH did you get?
My personal choice would be a 33x10.50. Two extra inches of differential clearance and less weight than a 12.50.
One other thing to consider: 33" tires will probably make you want better gears, and if you're doing the gears you might as well get lockers
(Just Empty Every Pocket)