You probably need a new bumper designed to house a winch. Or a custom made one. Don't think you can mount one behind the stock bumper anywhere. Could be wrong.
This, from a quick google search:
1998 Ram 1500 Short Cab Long Bed:
Weights: gross vehicle weight rating (kg) 2,903, curb weight (kg) 1,833, gross trailer weight braked (kg) 1,633, front axle weight (kg) 1,656, rear axle weight (kg) 1,769 and max legal load (kg) 996