[BR3W CITY]

I'd suggest lifting the truck up and seeing what kinda condition your trailing arms are. They can erode, the center of the stamped pieces can "Split" like old lumber.....yet remarkably still hold together. The more destroyed they are, they can allow flex and sway. You'll see some of the high performance guys stitch weld them to stiffen them up, box them, or replace them with tubular or fab unit (or just repro's).

Also, if your truck has the 85 front stuff with power steering, the pump will be spaced off the drivers frame rail anywhere from 1/8-3/4 of an inch because the frame wasn't setup for it originally. This will result in your steering usually going 1/4-1/2 turn LESS to one side...this isn't a huge problem for most vehicles, but the uneven center point can really screw with someone setting up the tierods and center link if they aren't aware of it from the get go.

I'd also suggest (as the others have mentioned) taking the truck to a higher-end suspension or alignment place that has the capability of taking the alignment in 3d space. "old school" alignments, and front-only alignments won't track ALL the axis on both sets of wheels; basically, you can be plumb/square from one observed measurement, way off on another in relation to it.

Most of the time the simple alignment is all you really need after a lowering, or to touch things up after potholes or something....but when you compound 50 years of history, at least one larger incident, lowering, and who knows what other repairs or changes over the years...its worth the money to know for sure. You'll be eating tires, and all around dangerous if your tracking poorly at highway speeds.