there's a LOT of difference between a 31 and a 33. the MJ fenders are all sized for a 30-31, not a 33. the axles are geared poorly for stock size tires, let alone 31s, and certainly not 33s. plus axle and ujoint strength starts to come into play with 33s.
are you sure an extra inch of tire radius was going to get you through whatever obstacle you wanted to try? lockers are more important than tire size.