Rapom's Rocket - just another Duster build thread
I doubt you would ever notice the difference on a stock suspension but when you begin lowering and stiffening the suspension for better handling these little improvements start to make a difference. Ucoog1, over on Moparts, has spent a lot of time and effort into doing just that to his Duster. He reported that when tightening the end links (compressing the poly bushings) that his front ride height would rise an inch in comparison to the bearing links. Makes a difference.
On a completely stock car the flat on the sway bar ends and the LCA sway bar tabs are parallel (in plane). As you lower the suspension settings the angles start changing and the flats and tabs start moving out of plane. The bearings do a better job of handling the angles vs the bushings and since the give of the bushings is taken out of the system the bearing links will providing an instant response from the sway bar to any suspension loads.
The K750074 end links are used on Ford and IIRC Dodge 4x4s so they are plenty HD for our use of them. They are just too long and need to be shortened (so far I have not found an application with shorter bearing links). To keep some factory engineering in the equation measure the lengths of your end links with them tightened down and try to mimic that distance with the bearing links. I had not considered the '72 and earlier design. I would think they would function very similarly to the latter versions.