I have the same basic truck as the op - classic silverado - I have the regular helwig rear sway bar - the big wig bar wasn't available at that time.
The helwig can be found on-line at discounted pricing. This will do the most for reducing sway. I found that airbags can induce greater sway if over inflated. I removed my airbags - but I have a 3500 srw. If I had a 3/4 ton - I would hit a spring shop or add some supersprings instead of adding airbags. My reasoning behind this is that springs are more "linear" than airbags - you compress airbags and they get stiff fast and can overcome the dampening in your shocks - starting an "oingo-boingo" effect.
jeff