Michael -- here is a link that does the full upgrade of the Harbor Freight 2 HP DC to a unit with a Wynne Environmental canister filter. Looks easy to me. Hope this is what you were looking for.
Here is another thread for updating the type of DC we have, taken straight from WN a while back.
Wynn now has a filter that doesn't require any special tricks to fit our types of DC, perfect match in diameter and a few turnbuckles to hold it down. I'll track down that link, too.