Can anyone give me some advice on where to get aftermarket gears (hopefully inexpensive) and possibly air lockers for a 98 D1? Also I run 33's all terrains, does anyone have advice on what gearing to use? I am stock right now although I don't know what the gearing is. I would like to go lower but still maintain good Hwy speeds and Mpg's. Thanks for any advice!

 

4:11's are what you need. Might want to talk to Bill Davis at Great Basins Rovers in Salt Lake City, he has been the expert on Rover drive trains for years.
By going to 4:11's you will actually regain mileage lost from installing taller tires.

 

Agreed with GBR. I'll be running their axle shafts along with Tractech Detroit/TrueTrack in the diffs. I prefer the simple "never fail" type product over the hassle of the air locker, but both are excellent options.