Many people are going to aluminum radiators--they are more efficient at dispersing the heat. I haven't had the need, i just use a 4 core. Ensure your shroud is directing the wind correctly and if you have a clutch fan that is several years old, check the operation of it--it may need replacing, especially if you have A/C.
Other than that, if you still have heating issues, raise up your truck some more, i hear it is cooler at higher elevations.