The OP says he is looking for something more HD.
Many of us pulled rv trailer 40+ years ago when most smallblock V8 gazzers pushed maybe 180-200 hp and maybe 290-300 torque. We pulled our 8k-9k trailers all over the Rockies up all the majors 10k-12k passes and down the other side. Those old under powered trucks had pizz poor brakes...small radiators....hot running auto trannies compared to what we have today.
IMO a 1/2 ton truck with a small block V8 or a V6 would be a good choice for a 4500 lb trailer in the mountains or worse yet in the flat lands fighting 35-40 mph head winds on all day runs.
