A CME lean hog contract is 40,000 lbs of carcass weight, NOT liveweight.

If you sell hogs that avg 270 lbs live and yield 74% you will have about 200 lbs of carcass weight/hd.     So it takes roughly 200 hd to fill a contract.

There is no "normal" basis.     That is what makes forward contracting hogs on the CME so unreliable.

Packing plant cash prices can vary from $5 or more over the CME to $10 or more under the CME.      

Basis varies by the season and varies a lot when the lead month changes.    Weather can have a huge impact on basis as well.