I second what everyone says. The billet drum and ultimate sprag are the biggest concerns so since you already have them, youre in good shape. I will add, put a steel front planetary in the transmission, aluminum stock front planets are know to strip out the splines. The bleed hole to the front drum needs to be done. Some put it in the piston but its recommended to do the drum. Once you do that you need to move the vent to the rear because with fluid escaping the drum through the bleed hole can cause a leak out of the front pump vent. I haven't experienced that personally but I know that is the theory. If you put the bleed hole in the piston opposed to the drum, you may not have to move the vent.

Definitely a steel stator in the converter as the aluminum one will absolutely explode. Being that its a street car as well, your gears are "harder" than a pro gear, so you may want to consider that before installing the trans brake. My richmond pro 4.56 gears have over 200 runs on them. My US 4.30 pro gear both sets lost pinion at 200 runs almost exactly. The richmond seems to be happier knock on wood. Like any race car part, they last until they don't.

As far as a button goes, I have mine on the steering wheel, but know others prefer it mounted elsewhere away from the wheel.

You are going to want to wire in a relay so that when the transbrake is activated, the line lock also activates so the car does not creep. If you don't wire in the relay which activates the line lock when the trans brake is activated, just stage at low of an idle as you can before hitting the button to avoid the least amount of load on the chassis. Once you activate the trans brake, if you are at a high idle, without line lock, the chassis will relax and car will rock forward.