Help with strange knock???

I would do the Rusty check first. If its not there, then; -When the front end was rebuilt, were rubber bushings used, and were the control arm nuts tightened at ride height? If the nuts were tightened with the suspension at full droop, then the the rubber bushings will be preloaded. this may be manifested as a slow to settle front-end. Then if one of the new shocks has a tight seal it may stick-release on the rebound stroke. This makes a very distinct sound(may not be heard with engine running) and I would imagine it could be felt as a vague knock in the steering wheel. You may have to jack the front end up(under the K) to prove this, but do not lift the wheels off the floor during this test, as it will not settle properly, if Im right. If poly bushings were installed the preloading may not be an issue,however its still possible that a shock is sticking. -Or a lower shock mount is loose or has excessive clearance.