I am thinking about doing the same with my 70 C20 coil truck. I just removed my overload springs that bolt to the frame and rest on the trailing arms. The truck rides a little smoother, but still really rough with an empty bed. I also want it to ride at stock height with bags in the rear to ride better.
My plan is to put the overload springs back on and then replace the coils with bags. The overloads will still support the suspension in case there is a blowout.
I will probably buy these mounting brackets
http://www.newmaticsinc.com/196_72_C...s_p/231156.htm
and then get slam specialties 7 or 8" bags. I just don't know if the 8" bags would be too soft at ride height in combination with the overloads. It may be a trial and air (error
experiment.