Ray,
Definately use an aluminum gear and not the original wire gear. Your LHS or Tower should have some brand of after market .40 size aluminum gear.
I purchased Great Planes brand at my LHS. Dont forget to buy the axles and matching collar size for the axles. If you don't have the larger wheels yet, but them too. (just match the collar, axle, and wheel's hole size). Wheels can be drilled out... carefully, to match axles. Wheels for grass at least 3 inches. With the size of the LT-40, 3 1/4" or so would not look goofy.
...lownslo..

PS. Some kits have bolts for axles. (a terrible hardware choice). The threads on the bolt will eventually "ream out", and enlarge the hole in the wheel.