What's a good starter suspension system that can be upgraded later?

Not sure I agree. My own is sort of a "work in progress." Where we are at right now was recently original front drums, just got through finally getting disk brakes under there. In between, went from fairly worn old shocks, to new but "so so" shocks, and from original T bars to some big ones out of a parts car, .9" or so. At the moment, I still don't have the sway bar hooked up. It's "next on the list."

From the start, somewhere in the middle, and to the "now," it wasn't dangerous to drive at all. Went right down the highway at 70 and with modern tires, certainly handled better than when it was new with 2.50 X 12" LOL original tires.