You have to drop the transmission to install the kit and for the TC install so why not do it all ? It's not that much more in cost for parts.
In saying that if you do a full Transgo with the main line pressure upgrade your transmission will handle additional 225 HP at the flywheel I'd imagine with some careful driving IF and I do mean IF you haven't done any damage to your clutches to date. With FRESH Borg Warner clutches you be fine as described.
There is no guarantees implied here