Medusa 36-80 or 36-70

Ok, I have seen some people running the 70mm in the EMaxx with no problem. I am wanting some advise on what I might need. I have the 3905 with MMM ESC, aluminum bulks, RPM arms, Moab 40 series tires, Axial beadlocks and hope to get the FLM V2 chassis soon. I am running 3S 5000mah Zippy Lipos and will also be running 4S. All I do is bash, my delima is that the 80mm (2200kv) is on backorder and the 70mm (2300kv) is in stock. I want to go about 40-45mph (that is fast enough). So, If anyone has a recommedation I would greatly appericate it.

Tim