newbie looking for advice

if you'll be out further than you'd like to walk back, I'd say go with the factory bike

there are nice two wheel drive and high dependability back country types out there

Hi,BDKeg. Your approach on extending your range into the woods by going with a Motorized/Motor-assisted bike is indeed innovative and probably a lot of fun! However, I echo Crassius's word of warning. Motorized bicycles are usually as much an ongoing hobby-type, art-project as they are a utility. Don't get me wrong, I usually put about 1,000 miles on my bike every year, I live in a semi-rural area with both city and dirt-road conditions involved in my work-commute. Definitely one of the best ways of getting around especially when cars are backed up at rush-hour. But, with all bike configurations being "custom," a gas-powered setup involves a perpetual risk of something popping off or failing. If you don't have tools and misc-replacement parts with you and you're way off in the woods you're not going to be happy. Then you'd be carrying all your hunting gear AND your bike down the logging-roads or whatever.

Given the description of your need, if you HAVE to go with a gas-powered setup I would recommend going with a 4-stroke kit, they are usually more dependable and less temperamental. Also, if you are dealing with carrying heavy loads you may wish also to install a shifter-kit. With chains flying while traveling super-rough terrain, however, there is a good potential for misalignment & broken parts. If you can afford it, see if you can go with an electric solution. Fewer moving parts and much easier to implement on a FULL-suspension bike; you can even make your mountain bike 2-wheel drive. Best of all, electric bikes are ninja-quiet compared to gas-based motors, the Elk will never hear you coming.