Welcome!
A sway bar will help a lot and it should be highly considered. Perhaps some good aftermarket shocks as well. Six-Pacs I believe are relatively a lighter weight camper compared to most of the members here. A 250 has at least some good components of which might need some basic modifications... but conventional wisdom says to put the camper on the truck and then decide if suspension upgrades are necessary.
There are two popular ways to attach the camper. The bumper to which you allude is part of a brand called Happi-Jac. This method of using the bumper as well as hardware that includes a tab that sticks out between the front of the bed and rear of the cab allows fasteners to attach from camper to truck. If the bumber is not that stout, I believe that HJ has stiffeners that can be added to the stock bumper. I do not own this brand and am not as versed in it specifics.
Another brand is Tork-Lift. This style utilizes steel brackets under the bed that are fastened directly to the truck frame. There are inserts into these tube-brackets that stick out under the "rockers" of the bed to which fasteners connect the camper to truck.
In either style, it is better to use spring loaded fasteners over the old style of just chains and turnbuckles.
