I'm going to be towing trailers with my Magnum R/T.

In the handbook it gives 2 different towing weights.
One relates to the 'Towing Package'.
Dodge tells me that this means a heavy duty radiator, transmission cooler and heavy duty rear springs, but can't cross reference any specific part numbers for any of these items.

Can anyone tell me where I can find any of these items?

And where can I find rear spring air bags to assist the stock springs?

Thanks - D