Which cars are you actually talking about? The history, if I remember correctly is:
RRR Evo WC
RRR Evo2 WC
Regarding changing your car over, here is what I would do. Change over the rear end so you can use zero offset tires. Mostly because the zero offset is easier to find. When you have to replace the chassis, you will most likely have to use the Evo2 chassis anyway as the older chassis is discontinued. I would do the same thing with the radio tray as well. Either change that over when you need to replace the chassis, or wait until you break the tray.. which may never happen. There are other differences, but I wouldn't worry about it just now. You seem to be a newer racer so practice is your friend. Put your car together and go run some laps.