Actually, the rear locker is a pre-selected option for the Z71, it isn't actually included in the Z71 package, still an option. The Z71 does have better bushings, large fender flares, and nicer shocks.
ANYWAY, yes, the Z71 wheels should work, they are 1/2" wider rims, and the tires are 275/75/15 I believe.
2006 Colorado, I4, 5-speed, extended cab
Pontiac Grand Prix leather seats (power)