Looks like a standard trailing arm, coil spring, with panhard bar. A lot like NASCAR uses, just not as beefy. Early 60's to early 70's Chevrolet two wheel drive pickups also.
Alot of light weight trailers from the 60s / 70s came that way especially boat trailers. I got one give to me like that, it was in the weeds at a guys house for years. I was going to use the trailer axle in a project but it was way to light duty.
That's super similar to what I want to do to my trailer to eliminate the short length leafs. I'd use snowmobile coilover shocks as they are adjustable for loads.