Heim end clank, clunk, and jingle constantly down the street. They are IMO made for racing. I had a '34 coupe with a blown 514" Motor in it. Front and rear suspension was all Poly bushed ends. I like long 4 bars on the street, at least 24", mainly to allow the geometry on the rear end to remain more constant. Rear 4 bar on a drag car is an entirely differet world. On a drag car you are only worried about hook and weight transfer, on a street car you will blow the tires off it long before you hook it hard enough to realize any adverse effects from poly bushings.