64 dart shock upgrade

Depends a lot on the rest of your suspension. If you have stock, or less than 1” diameter torsion bars then you probably won’t notice much difference going to the Bilsteins, although they are a much better shock. A regular old set of Monroe’s would be fine. If your torsion bars are bigger than 1”, then absolutely Bilsteins or Hotchkis Fox’s.

Just avoid KYB either way, unless you want your car to ride like a dump truck.