2wd micro construction rules

[dodgydiy]

i built a 2wd prototype a while ago using rc18b parts, recently saw it mentioned that a 2wd has to have a stacked gear gearbox, mine has the rc18 gearbox which is not a stacked gear box, does this mean it is not raceable any more, i try and build my cars to race, even though it doesnt happen very often. i know my converted tc3 would be fine under 1/16 rules but i have always liked 2wd and would have liked to have a go at it. as i said the car is rc18 based and of very similar dimensions to an rc18 so would fit into 1/18 scale, if it is not legible to run as a 2wd, can it be run in a 4wd class?