Tardog, I just noticed this thread. Sorry.
the shackle flip pic you posted is from Shaggys 4x4. Bill Cooke knows his stuff. he specialized (I say in past tense because he is now doing it on a "special order" basis only) in dodge stuff, but only 72-93.
Shackle flips have some advantages and dis-advantages.
First, you can get better ride quality with a shackle flip if it is designed correctly. Compression shackles will usually allow more spring travel than tension type shackles. you can usually get about 3" from just flipping them. I have two trucks with the flipped shackle setup. one is a 74 and the other is a 77. They both change the truck dramatically. Both hook up better on the street and dirt. Both articulate much better, and there is less axle wrap (shorter blocks). One has both the 3" flip (from shaggys) and 4" springs. the other is just 3" flip (I made it).
I have towed pretty heavy with the 74. Well, as heavy as you wanna tow with a small block and 40" tires (7,000lb trailer). It towed perfectly fine (again, as good as 40" swampers will allow).
If you are still interested in this and want more info, I will post more.
--Jeff