Just saw this thread. Where are you now with it? Hopefully finished. If not and your still worried about moving the cherry picker in the snow just move the car instead. Can be pushed by one if your strong enough or two or more (better). Immobilize the hoist on 3/4 plywood,( nail stops in front and back of the wheels or cut out holes just enough to catch them if its not level enough) Then cover the front of the car with visqueen (plastic sheeting) or something like, or put the hood back on, And either take the engine into the building or build a temporary shelter around it. Doesn't have to be too complicated or large (its disposable) Could tack plastic to the front of the building. If you use the clear plastic you might be surprised how warm it will get in the daytime, don't seal it up tight, leave a few cracks for ventilation. Run a drop cord for power. When you stop the wind its much warmer. But the propane sounds good as you will want to warm up the metal a bit before torquing any bolts on the motor. Long before you could get or borrow things like cherry pickers easily we used a tripod (sometimes made from a swing set) and a chainfall and pushed the car back and forth. Thats why it took at least two. Needed someone to watch when you pushed the car back under the motor to keep it lined up and from hitting the windshield. (or to take you to the ER if you forgot to make sure that the setup was solid and dropped the motor on your foot or something else necessary) Save the beer till the job is finished! That way the help wont be crashing out beside the job and you wont have to drag em inside to keep them from freezing to death!
BTW that dropoff looks like a good place to build a oil change/lube rack. Just build it to bridge standards. (and put good stops on it)