under seat box for chevy questions

[Blue Chevy Man]

I'm fixing to start my adventure in making my first floor conformed box for my 2000 chevy silverado and am not sure where to put the sub or port

1. I'm not too sure if there is a difference between an L ported box and slotted box sound quality wise or loudness wise

2. I'm stuck on weather to make the box a down fire or "seat fire"

3. I'm also stuck on how far down on the back wall to place my amp and what to hold it up with