When I kept having problems with 4 spd. shifter hang-ups on my 64' Impala SS I crawled under see what was up. Sure enough, several nuts were loose on the linkage bolts right on the trans. While trying to tighten the nut on reverse, the bolt broke off! I can barely get a nut on whats left and that's w/o a lock washer. How do you remove that bolt (stud) and replace it? Can it be done externally? Any info/advise is appreciated. As a last resort I can get thinner nut, I guess. thanks.