The fact that these trucks have four rods and a belcrank between the shift box and the tranny doesn't help either. All those holes get "egged out" after time. You can tighten things up by welding up the holes and redrilling them to fit the rods better or drilling them out a little more and finding bushings to make a snug fit.
It's also good to learn "square shifting" technique. You couldn't speed shift these even when they were new. To square shift, you do the ninety degree turns in the shift pattern. To shift from 1st to 2nd, for example, you go up to the gate, sharp right to cross the gate, sharp left, then up into second. Trying to cross the gate on the diagonal is an invitation to jamb up between gears.
