Your right about manual, just did not see the need to auto inflate. Ran the tubes out the license plate top holes so no drilling and worked perfect. I tow a 21 foot fish and ski and just needed a little help. Also feels better when not towing. I keep them at about 20psi.
Not sure of the offset or exactly what lift. There is a local guy that does lifts for the local GMC dealer that maintains warrenty. Tire size is 305/55/R20 and they do not rub.