I'm going to be ordering a 4 stroke engine kit off of Bicycle Engines, Motorized Bicycles, Bicycle Motors, Motored Bikes: 2-Stroke & 4-Stroke Kits! and I want input on both 4 stroke engine kits. What one lasts longer? Less problems? Etc 4G T Belt Drive 4 Stroke Engine Kit 49cc 4G T Belt Drive Complete Gas Powered Engine Kit - $379.99 VS. The Skyhawk Stage III Whopper Stopper 49cc Complete Stage III Gas Powered Bicycle Engine Kit - $369.99 Also I'd like input on websites that sell the engine kits, and how the service is. Thanks!