Originally Posted by Mike B
Take a chance, roll the dice.
Let's see if we can help the man.
We suggest that instead of price and power claims that you order from a reputable vendor. One that will stand behind his product. As for power and reliability, there is very little difference in these engines. Some will offer upgraded parts in the kits such as twist grip throttle, clutch lever etc. but for the most part the kits you see advertised either here or on ebay are identical. 35 mph is attainable but realistically you should expect something like 25 to 30 as a more reasonable expectation with a stock engine and the typical kit supplied 44T rear sprocket.
I hope this helps with your decision.
Good luck and we're always here to help with your build...at least most of us are.