trans 727 n 727 lock up

Hi i wanna know what is the difrerence between a 727 and 727 lock up trans cause i wanna change my 727 by a lock up. It's for a diary car, not for a track... well some times i like run but only street ...and i think to my 727 start to fail because when a i put 2nd to 3rd gear (manual) to 1700 rpm, just goes down to 1500. and a 44 miles, i go to 2000 rpm i think are many rpm
Thanks i appreciate so much you comments
Regards

You can't convert a non-lockup 727 to lockup, the case is different.

I know , i want change my 727 by a 727 lock up ... the 3rd gear is more larger is better for a city car!!???
thanks anyway