As a fellow mere mortal I agree entirely Dai. The idea of buying a RTR model and then effectively discarding the entire chassis and mechanism and replacing with a kit or scratchbuilt chassis and new motor/gearbox has little or no appeal for me. What I wish to do is exactly as you describe. I do not mind having to buy new wheels if that is necessary. So, any info I can find on the feasability of relatively straight forward conversions is always welcome.