Safe to assume you're looking to get Pax into pulling and not Jimmy right?
I'd go for it personally - mind you, don't hook the dog up to a 500 pound sled and expect too much to happen. Start off slow, dogs are generally pleasers and any job they can do for you is rewarding. If you have kids, pulling them in a cart is rewarding.
I have a friend with 3 kids and a lovely pitbull something, weighs about 70 pounds and solid muscle. They go for walks, the dog pulls the kids. Dog burns off energy, and seems to love what he does.
I did some for fun weight pulling with my first dog. Mostly it ended up being more like carting in that it was just low weights around the yard, neighborhood, etc, as that ended up being more fun for us that pulling larger weights over short distances. It is a good way to condition your dog, and can be lots of fun to use if you have kids around, as they enjoy going for wagon rides with the dog. If you decide to have your dog pull any significant weight, a well fitted weight pull or carting harness is important, as they will distribute the force in a more safe/comfortable fashion. Before investing in that, I would let him drag a milk jug with some rocks in it (just a few to make noise) to make sure he will be ok with towing an item behind him. You can d/c him to this, or if he's normally a pretty unafraid dog, just do the empty jug, then add rocks.
If you are conditioning to do serious weight pull, or just do condition your dog in general, most people use a weight pull harness and lengths of chain +/- window weights to drag, but you can also use a cart/wagon, just keep in mind that a cart will continue to roll and bump your dog's butt if you don't stop it (or use a carting harness with shafts, but those are for lower weights).
Ideally, you could go to a show and meet some people doing it, then try to train with them. Make sure to avoid people who get their dogs to pull by baiting (toy, etc), as this tends to be a less safe method.