Early Classic Enterprises does as well. Choices are shackles, drop springs, drop springs and shackles, or flip kit.
I flipped mine with a DJM kit from Summit Racing. Probably the least expensive method also gives the most drop. My truck has the 4 leaf + overload setup instead of the 3 + overload base spring so may have had a little more arch than the standard setup.
I pulled the overload because it was interfering with the CalTracs. And speaking of CalTrac, in addition to the traction bars (flipped or not flipped) they offer their split leaf spring as well I think. If you are going to try and make big power, I'd go with their spring and the CalTrac bars.
I did 2 1/2" disc spindles in the front with 2" springs for 4.5" drop in the front and the flip netted about 7" of drop maybe a tic more in the rear.
