Air bags and trailing arms??

[72kool]

This may be better in the suspension forum, if so I apologize. I have a '72 C20 gmc with rear trailing arms and coil sorings. I am replacing the trailing arm and need new springs. I am thinking about bags instead. I tow a lot with this truck so first, is this a good idea? I don't see why it wouldn't be. Better ride qualty, adustable load stability.. Am I wrong? My second question is, what/where? I read a thread on the install but unsure where to buy them from. I want a kit that will hold up to the extra weight from towing and be suitable for a smooth ride.