Automatic transmission strength

[pgoughary]

Hi, all. My name is Phil and my g/f and I have a 1989 mkiii Supra, N/A with an automatic transmission. I've grown up with a family of race car drivers and for the past ten years I've been playing hard with VW's and Audis. Elena (the car's current owner) is going to be getting into something a bit newer soon, and we've decided that we just can't let the Supra go. From the first time that I've sat behind the wheel of the car, I've been in love with it. I think that it has huge potential (it's in fantastic shape as is) and she's going to hand it over to me soon. The plan will be to make this my newest project, and I plan on it taking a few years. I'll start by tearing it down to as minimal condition as I can in a small shop and work from there (the work will include either a total engine swap, or changing the current block to forced induction - but I'm still researching all of that). My first potentially really dumb question is this:

How much power can the automatic transmission handle (rebuilding the tranny is also an option). She doesn't drive stick and I would like for her to be able to take her first car (yeah, she learned how to drive in this gorgeous '89) out for a spin without worry. I think that I can convince her to let me start the five speed lessons, but if the auto can handle decent torque going through it, we might just leave well enough alone.

Thank you in advance for your help and advice.