Remove the clutch for plenty of room. Remove the shift lever and shaft. Inspect that the shifter star is installed properly, and there should be 2 spring loaded detentes that hold the drum in position. Think about which way the shift shaft turns the star and drum, rotating 1 of the trans shafts will help to get it in neutral. Hold both shafts, they should turn separately. At this point make sure the star is centered toward the shift shaft, and install the forks on the shaft centered with the forks on the star. The case and shift lever hold the shaft in place, it only needs to move an 1/8" and it will not be engaged. Sure hope you have a shop manual, if you know you're way around, a parts micro fiche can help. Vintage Bob