['63GENIII]

B52's in front and 63's out back with a shackle flip.

My fronts are 52" out of the rear of a 1973 half ton K series. They are just a tad soft IMO. Sway bar is mandatory.

The rears are 63" out of an '07 Silverado and although super smooth, could probably use one more leaf. It gets onto the overloads fairly easily when loaded with 3/4 ton of rock.

In your case, Id look for rear springs from say a 96 or 97 Burb. as they would likely be better set up for your normal weight (not pick up truck weight).

DIY, ORU and ORD all make what you're looking for although I have found that DIY builds their stuff as if it were going under a tank or big rig. Super stout and great hardware.

I also think that both Bilstiens, FOX and the like have been designing their product for the newer, more compliant suspensions found on modern vehicles.

When I had the stock springs in the '63, it rode real stiff. I got a set of Rancho 9000 adjustables. Didn't make a whole lot of difference. I do like the 9000's for the new longer springs though. You can really feel a difference when the adjustment is changed.

Whichever way you go, take your time, take lots of measurements and lots of pictures!