THE MOTOR THERE LOOKS LIKE 99% A 440 BECAUSE OF THE COOLING TIN IS SQUARE,AT THE LEFT SIDE OF THE MOTOR, WHERE THE AIR BLOWS OUT. THIS WAS USED ONLY ON THE 440s. MOST LIKELY INDICATING IT IS A 440, KOHLER AND THE FACT IT IS A DUAL CARB MIKUNI VM SLIDE CARBS VERSES THE PUMPER STYLE. they may have pulled the tag off a 340 original motor. That engine there comes from a mercury snow twister snowmobile. and is rated at 55-H.P. That thing will absolutley fly, over 120mph. the 340,s put out 27 H.P. which your almost double the stock. here is my email for any further questions.
trisportman@gmail.com Mike.