go 36's+  I run 37's on profields (not really any stronger that stock) and I haven't had a problem.  I'm running the same duals 2.28x2 with 5.29 and f/r lockers.  Love my tires wouldn't ever go smaller now.  I'm not sure what in the drivetrain will have a problem with those tires except for the birfs and you already said you have longs, so go for it