The stock axle usually is shorther than the drop axle. They make the drop axle longer to give the cart a wider stance. Is your cart toed out like this? If so you need longer tie rods but the kit should come with them.
The Workhorse and MPT are identical minus the name. Yours is like a Workhorse 1200 not a Workhorse ST 350 though. Different models and front end setup there.