i know it sounds funny, but as i search for used trannys, i see where i'm asked: A.T., 4x4, 6 cyl, Calif, from 6/99
A.T., 4x4, 6 cyl, Calif, thru 5/99
A.T., 4x4, 6 cyl, Fed, from 6/99
A.T., 4x4, 6 cyl, Fed, thru 5/99
Look on the driver side door jamb. It will show the manufacture date of your truck. You might also need to look at the Emissions control decal in the engine compartment. That will tell you if it is the California version or the Federal version.