I've found them mostly under 87's, with or without the tow package, and both stick and automatic. I think it depends somewhat on the area you live in. In CA I've only seen them in 87's, and I've never seen an '87 without one.......but that's just my experience.
Many long bed MJ's also have a D44. The spring pads are under the axle, but it's very easy to weld on new spring pads on top of the axle. They also don't have shock mounts since the shocks mount to the spring plates, but most of us move the shocks up even with the axle anyway, so that also is no big deal.