GM-GMC: Suspension interchangeability?, chevy silverado, firestone ride rite

Question
Hi, I was wondering if you could help me.  I have a 1989 Chevy Silverado K1500 4x4.  I know your expert description says diesel trucks, but I figured I'd give it a shot.

I've gotten a job that requires me to use my truck for some heavier hauling.  I was wondering, do you know if the 3500 series leaf springs are interchangeable with my K1500's springs?  Or would I have to do some modification to make the switch?  I have the heavy duty option axles on my truck, I just need bigger springs to help haul the heavier stuff.  

I greatly appreciate your time!  Thanks so much
Sincerely
Fred

Answer
The one ton springs will likely require that the spring mounts be cut off and replaced with the one ton spring mounts to use them on 3/4 or 1/2 ton trucks.  You should be okay with the heavier 3/4 ton springs, if that helps.

On my G-20 3/4 ton van, I installed Firestone Ride-Rite air springs.  I can carry 5,000 pounds with the air springs, though I don't think that such a load would be good for the axle.  I use them when carrying and/or towing to keep the vehicle level and to reduce sway.

Carrying/towing weight over the manufacturer's recommended GVWR is dangerous, mainly becuse the brake system will not stop an overloaded vehicle in a normal braking distance.