3speed problem: clutch does not engage

[ReidCagle]

Any help is appreciated. I recently put headers on my 68. 350/3 speed on the tree setup. Had to remove the z bar and relocate the clutch rod bracket to clear the headers. Reinstalled and everything worked fine. after driving the truck twice, the clutch stopped engaging completly. There is no pedal pressure at all but the fork seems to move freely when viewed from below. Shifted fine when i drove the truck after the header install... has the clutch took a dump or is it a problem with internal components? I am in no way an expert on transmissions.