The problem with unassembled project cars is How organized was the diassembly. Did the person who removed all the items bag and tag them so you know where they go? The process of assembling a car is hard enough even when you know where the stuff goes. I do not understand your question about the 3 speed and what gears to keep. If you could maybe rephrase the question with some more detail and your preference of automatic or manual we could suggest a solution.
Ryan
Ryan