Since it runs, I'd change the oil, run it and use a fogging storage spray through the carb. Apply the fogging heavily and shut the engine off when it's stumbling. This will coat most internal surfaces with oil, like intake runners, valves, etc.
I'd then drain fuel or remove carb and seal any openings with a heavy tape.
I'd remove the plugs and add a thick oil to each cylinder and hand crank a couple time and put plugs back in.
Hopefully you have antifreeze in it and you can just drain any that comes out conveniently.
I'd then brush coat the exterior of everything with clean thick oil, put the whole thing in a cardboard box and store...
Dean