As long as height/width are the same or close to,, I don't see to much of an issue. The biggest part will be to get the front clutch/pto orientated in the correct locating.
If you used a base plate, made to fit your craftsman motor, sized to fit onto the existing tractor frame, it sure saves a lot of grief. An added bonus is if it's say 1/2" shorter in height, you can add a spacer between frame and new motor plate,,,
The big one is to orient the crank, so it sits in the same relative horizontal position as what you take out. (Saves a lot of guess work with belt sizing)
1.) front side of engine will accept the PTO for the mower/snowcaster. (will it bolt on?)
2.) rear crank will work with the pump
Does it have the proper diameter shaft. Could you get around this by buying a Lovejoy coupler that fits the engine crank size and also mates to the existing pump Lovejoy? Perhaps. One would need to check the catalog
Is the shaft of proper length. (1.3" +/-) (Could a long shaft be cut off? I suppose)
Does the pump side have holes suitable for mounting the Lovejoy housing?
3.) Can you deal with whatever is necessary for exhaust routing?