4spd shifting difficulties

The trans has 68k on it, but the car was seriously drag raced. 12.5 to 1 ,big cam,blowproof, d/s loop,4.56 gear, that sort of set up, so I know they were`nt easy miles. I`m thinking synchros too, but I was hoping someone would tell me something else. I`m running 140w in it now per the manual and recently drained a quart and added a Lucas treatment.It didn`t seem to make any difference. I hope I don`t have to rebuild it ,but I`ve had to rebuild everything else ,so it would`nt come as a surprise.