I'm finally getting my tranny rebuilt after living with it slipping for a few months. I already have a shift kit and a high-stall torque converter installed but will that be removed once the new transmission is installed or would they build that in with the new tranny?

You need to tell whoever is doing the work what you have done and how you want it to shift when they are done.

You definently need to go with a new converter. If the tranny was fried the old converter will have metal shavings in it which will find their way into the new trans. Also, make sure that the cooler lines get flushed out, for the same reason. Dave