Just went thru this on my '72 D100 & decided to just do a mild amount lowering to take the fender gap out & keep it so I can still use it as a truck. I am running a 28" tall tire on 18's.

On the rear I went with a square body McGaughys rear lowering shackle which lowers it a little lower than advertised for the GMs because the factory Dodge shackle is shorter than a GM.

On the front I cut 1/2 a coil out & it took it down a little over 2".