Re: Mountain or Cruise?
Walmart Schwinns aren't necessarily of the same quality as a higher-end Schwinn cruiser. For one, they are already a low-end model. Two, they might use inferior small parts compared to the same model sold elsewhere (yes, it's happened). Three, they are assembled by a guy who gets paid based on how many he can assemble in a day. Quality is likely the last thing on the assembler's mind, and it's probably not on yours either if you're thinking about buying a Walmart bicycle. Let alone putting a motor on it. Expect to rebuild all the bearings and upgrade parts immediately.
According to the manual for the Honda GXH50 that the Huasheng is largely based on, the motor can be at up to a 20 degree angle. I don't think you'll have a problem there. I worried about the same thing when I built my bike, because in order for my engine to fit in my frame with the shift kit mount (it sits higher), I had to mount it at an angle. It levels out when I'm on the bike, but I was worried at first. For nothing, I found out!
Yes, the shift kit does work with the 4G. I have one, ocscully has one, and MotoMagz has one. However, we're all using the narrower 4G, the Honda-style version. You can also use the standard 4G, but you might have pedal clearance problems on the left side. The regular 4G is 1.5" wider. You can get around that with shorter crank arms or ones with more offset to them.
If you want to see how a shift-kitted 4G looks, I have a photo album on my profile page. Any more questions, we're all here to answer them!