1991 camaro v8 305 shift kit A few questions about the best options for my car.... i just dont know?

Can i get a better trans for this car and keep my speed? or poss. reduce the slam somehow.? I know that the shift kit is made that way to slam quick 'n go fast, but im looking to rebuild my engine. i want something .... to match the new engine. Would it be better to get a whole new trans? and what would give me the same results on performance as my shift kit does?