My 1994 Thunderbird has slight 'thunk' sound and feel when accelerating from a stop.?

It almost feels as if something is slipping into place on the driver's side front. I just had the McPherson's struts and shocks changed, new tires, alignments, new springs, etc. Can anyone give me some clues to what it might be, and if it's safe to drive for a few more days...I know the answers will only be guesses, but I hate to walk into a garage without some kind of idea.