He likes using the low 1st gear set.......Mine has that was well......AND I would not re use the old convertor. Good chance to have debris in it and there is no way to get it out...... JMO.
If it came out of a perfectly working transmission, then maybe I'd use it. BUT yours came out a transmission with unknown problems. Who know what is in there....AND if there is anything in there, it wont react well to your new transmission...Ask me how I know....