There is a farm near us which uses Suffolks as their power. It is called Horsepower Farm, and is located in Penobscot, Maine. Mr. Paul Birdsall owns the farm and is quite knowledgable. Perhaps he could answer some questions for you.
Also look up Jason Rutledge on Facebook, he has a very nice stallion and a few mares and uses his Suffolks in his logging operation and to run his sustainable farm. He lives in VA... I've chatted with him a few times, he's a nice guy. Been thinking about buying a team of fillies from him
Mainelydraft is spot on check out Jason Rutledge, but it might be easier to initially talk to him - the Suffolk Punch
Some other names to track would be Rodney Read, Doc Hammill, John Hammond etc.
If you do a search you will find a lot of farms have gotten out of the business in the last couple of years partly because of the economy and partly for other reasons. One of the big ones the Bar B in Emigrant Montana is completely out of it so if that pops up in your search then keep looking. Suffolks are a very special breed, very cooperative, hardy, and seem to be a little easy keeper than some of the other breeds. Also know, that there is a big difference in what is happening in their homeland (England) as far as breeding etc than the general approach here and in Canada.