I believe the Deere motor is the same, but the PTO end of the crankshaft is too long. The wheel horse motor, I believe uses the wrong oil pan to be used for the Cub...... and if that is correct, the blocks are different and a shallow oil pan won't bolt to it.
If that is incorrect, I will stand corrected. I am going off vague memory.
If I am right about the Deere engine..... you could just get the correct crank and swap it. Should be able to get a ground 16HP crank for less than $100
What is wrong with the original motor?