Re: Long trip planned-- advice welcome!
If you want reliability and simplicity, you should be doing a rack mount friction kit. You can save some money by using a Harbor Freight engine. This will give you more flexibility about which bicycle platform you use, since you won't need to worry about mounting in-frame. It also eliminates the complication of an additional chain and sprocket. And it won't cost too awful much more than a HT two stroke kit and all the incidentals you'll need for it, and all the hassle of fooling around with it.
Just put a bunch of extra tires and a gas can in your trailer.