Any idea on weight?
Are you looking for new truck or used truck? Makes a difference as payload has increased significantly the last few model changes.
Without knowing either, my recommendation as probable best fit will be a Ram 1-ton SRW. The bed shape and cab height are the closest to the old trucks made back in the late 60s so fit would probably be easiest. The SRW has a 4,300 payload capacity. If you need more payload, go to a DRW Ram though it has slightly smaller tailgate opening which may or may not be a problem.