I believe it could be a number of items but in order of importance I'd check

Lower Ball Joints
Radius Rod Bushings (yes I do make the best replacements)
Tie Rod Ends (but if it's up and down it's less likely)
Front Shock's for Bump setting then Rebound
Front Springs should be 500lb to 800lb rate depending on your driving style (with rears going from 750 to 1000 in proportion)
Upper Spring mounts (perhaps)