This GMFK25S Timbren kit works by contacting the lower control arm to offer support for extra loads in the front of the truck. With a lift kit the lower control arm will be pushed away from the Timbren and it will not be allowed to contact. If you lift kit has some form of bump stop extension that retained the factory spacing this kit would work as usual but if the distance between the bump stop mount and the control arm is farther than stock this kit will not work as intended. It may be possible to order a custom kit with a larger rubber Aeon to accommodate the extra spacing but we would need a measurement of the distance between the bump stop and the control arm with the truck sitting unloaded, on level ground. We could run the measurement by the techs and Timbren and find out if a custom height kit would be available.