Muncie 4 speed

Ok can anyone tell me what Im doing wrong? I have a 64 chevelle with a 383, 4 speed, and 3.73 gears. it seems that I have trans problems more often then I should. I put a new center force clutch, presure plate, throw out bearing on it abouta year ago. first I had a problem with the throw out bearing. replaced that then the trans had a bad gear. had the replaced. just a couple of weeks ago It started to make a nosie, pulled the trans found the throw out bearing bad, also the front bearing on the trans was bad. replace those items amd now a week later there is a noise in it. pulled the trans and find that it has a gear with two broken teeth. why am I having so much trouble with this trans am I missing somthing? could it be that the trans is not centered in the bell housing? (lakewood blow proof) it also has a roller bearing for the pilot. should I change that? help im getting tired of pulling this trans! thanks in advance for any info