I prefer 31-32" tires on SPOA Samurais. Much easier on the axles, drivetrain and they fit the wheel wells better. If you haven't bought the tires yet, look at some 31" or 32" tires. Bigger is not always better.
Anyways, to fit 33" tires, you really do not have to do anything to the rear axle other than massage the seams a little. The front will need the front axle pushed forward an inch and you will need to massage the seams and possibly rework the inner fender near the front of the fender.