What vintage CJ? My rule of thumb is that 31x10.5's will fit with no lift on most CJ's and I don't think that would change with the wider width. You will need wheels with shallow backspacing, someplace from 3.00 to 3.25" to keep the tires off the front springs and you may need to reset the front axle stops even then. If you go bigger than 31's, yes you will need a lift. 2.5 to 3" generally to run 33's.
1947 CJ 2A, 1949 CJ 3A, 1955 CJ 3B, 1968 CJ 5, 2012 JKUR