I got the 3523 base plate and new worm gear. It was the correct base plate. I cut the worm gear the same lenght as the old gear and screwed it in with the antenna in the down position. Put some plumbers putty on underside of base and screwed the base down. What's strange is that the hex end of the worm gear sticks down through the roof too far now and I'm going to have to cut off some more of it. I screwed the new worm gear in tight. The old worm gear wasn't screwed in that tight. Maybe that's the reason for the extra lenght. I checked the operation of the antenna, and it raises and lowers fine. After I cut some more of the worm gear off, all I'll have to do is caulk the base plate, and I'll be done.
2008 Rockwood 8265S
2006 Chevy 1500 Ext. Cab LT w/5.3V8 & Tow Pkg.