Ladders aren't really "street friendly". They pretty much force to rear axle to move up/down in one plane, which is OK as long as the road is dead-flat. Put some bumps, potholes, ripples, etc in there and there will be binding. Will they go over bumps? Sure! But something is gonna flex that shouldn't be flexing, which will eventually lead to breakage. Usually at the most inopportune time. Even with spherical joints, because the ladders themselves are triangulated, you cannot overcome the fact that those joints are forced to operate in only one plane.
The only issue with strip type 4 links is that you have to raise your floor where the rear seat is to weld in the front bar they bolt to.Many people don`t want to do quite that much fab work.
