I'm lowering my '84 D350 Crew- not ground-scraping low, just enough that it doesn't look stock. I already modified the rear spring hanger to lower the rear about 2 to 2-1/2 inches, and I plan on relocating the front hanger for an additional inch.

On the front springs I've been doing some investigating.
The Moog stock HD D350 spring shows these specs:
.90 bar diameter / 13.13 installed height / 1725 lbs / 1144lbs-inch.
The Moog #7170 stock D250 spring shows these specs:
.810 bar diameter / 10.5 installed height / 1815 lbs / 845 lbs-inch.

From these measurements I''m assuming I'll get a more comfortable ride, and I should end up with just over 2-1/2 inch drop just from the difference in installed height (my D350 has pocketed lower control arms), and approximately one more inch additional drop due to the difference in spring rate, for a total of about 3-1/2 inches.

I don't have much experience with this sort of thing, and just thought I would get opinions from folks who may have done something similar. Weird that the total capacity of each D250 spring is rated 90 lbs. higher than each D350 spring...