727 shift kit?

They do sell shafts but the play is probably in the aluminum of the case or valve body and not actually the steel shaft.
If it's a little sloppy while in the case then it's possible the case is the problem.(depends on definition of sloppy)
They also have a "shaft saver" seal that rides on a different spot on the shaft to solve shaft groove issue's.

The TF2 kit is a personal choice, unless you are putting out more than stock Hp numbers.
Shift kits can shorten the time it takes to apply clutches and other friction surfaces and lengthen the lifetime of a trans.
If over done it can also unnecessarily increase stress on parts like planetary gear sets, sun gear shell and shaft splines.