I have not had ants in my pickup camper, but I did have carpenter ants in my 4th wheel. for that we use this bag from terro that you shake solid crumbs out of to create a barrier around the RV. that solved that problem.
in our house we get those little black ants some times but the terro liquid ant baits takes care of them. Now I set up the liquid ant baits outside around the house and it seems to draw the ants away from the house :).
Part of my setup for the pickup camper has always been to spray Raid on the jack feet, around tires and wires.