YES. One of the best modifications you can make- not only will it get you out of the hole faster, but it will free up ~5% of your horsepower that is now being lost in that big old stock converter.
Having a higher stall wont hurt the tranny or engine. How old is the converter? It the person your getting it from has bought it from them within 2 years you can have the stall changed free of charge + shipping. If it's after 2 years they shouldent charge that much to change it.
I would give PI a call and see if they would set the stall according to your mods and re-warranty it, of course, finding out how much they would charge.