There is a lot of confusion. In a '73-'87 truck; going from factory height front 47s (0" lift) to factory height rear 52s (0" lift), one will gain 4". In the day (when 52" spring swaps were ju-ju) the typical axle swap brackets (ie. ORU, ORDirect, ORDesign, Sky, etc) give a certain amount of lift over a factory height '88-'98 truck (we'll stick with that since this is GMT400.com), ORU: 3" I believe, ORDirect: 4" I believe, ORDesign: 3", Sky: 6" or 2.5". These previously mentioned lift numbers are calculated from using their brackets with a factory height (0" lift) 47" spring.
So, if the 52s add 4" in a '73-'87 truck, and the '88-'98 axle swap brackets give anywhere from 2.5" to 6"; in theory the minimum lift one could achieve is 4" over what the brackets advertise giving.
In my truck's case (and the few out there with my brackets), the trucks have averaged 6" of lift when using factory height 52s (0" lift). If 52s give 4" of lift automatically, my brackets only incorporate 1" of lift. To be more specific, and scrutinizing my truck, I have the 6leaf spring pack (with no overload (less leaves would yield less rate, equaling less height)) and my spring pads are 1/2" taller than factory; if I used a '79 D44 with a very typical 4leaf pack, I could have had a solid axle truck nearing 4" over stock. I know we're splitting hairs here when saying I could have dropped it an inch, but I'm just throwing out options and possibilities.
Sorry for the book, I hope it sheds some light to people and gives some good tech.