need help wont shift into third

unless I missed a sentence or two, you have not said that reverse is good, ok or weak on apply. This clutch pack is the same as 3rd gear. So if reverse is good, then it is in the valve body as suggested by others....more than likely. Did the trans shift prior to this? Has it been rebuilt? Did someone install a shift kit? A bit more info may be helpful. Good Luck. Valve bodies are not that bad to work on. Especially the 60's and 70's vb's