On the tank:
You better do some fiberglassing of atleast the joints. This is going to be the site of failure most likely as the joint will want to move under load and as the wood swells/moves (wood does that based on humidity, etc, etc, etc...and there's no way around it. Research fiberglassing, and make sure you use fiberglass that's ok for tanks.
Either fiberglass the whole interior (I'd recommend it), and/or use pond liner. Both cost a big chunk of change.
Make sure you use thick enough glass or acrylic for your viewing pane. There's online calculators to get the thickness. It's going to be super thick, and SUPER expensive for a 40" deep tank. I think once you see how much this piece of glass is going to cost, you'll go with a shorter tank.
Honestly, you'd probably just be better off buying a 480 gallon acrylic (8 feet long X 4 feet wide X 2 feet deep). They are about $2k from a reputable company like midwest customs. That's about $1k more than it's going to cost you to build your own, and you won't have to worry about flooding your parents basement. I'd SERIOUSLY consider this if I were you.
You're going to need some serious filtration on that big of a tank as well. Read up on sump designs. My favorite is a 3 chamber sump. 1 chamber with the inlets going into filter socks. 2nd chamber is a wet/dry trickly filter stuffed with pot scrubbies, and I use an acrylic drip plate drilled appropriately. 3rd chamber is proceeded by a bubble trap and the chamber houses the pump. Make sure you leave enough room in the sump so that the back wash in the event of a power outage and the pumps shutting off won't flood over the sump.
As for your stock:
I'd read a lot in the ca/sa cichlid forum if I were you. Please don't post a bunch of threads in there. Just read, read, read, and read some more. There's already a lot of threads about species you have in your list.
What I would do is start with juvenile fish, and as they get aggressive, sell them. That'll leave you with the more passive/community friendly fish. And ca/sa cichlids that grow out together work out together much more frequently than getting bigger ca/sa cichlids and just putting them in a tank together.
Also remember that ca/sa cichlids that form pairs can kill a lot of fish even in a big tank. And your 8'X4' tank won't be big enough to have that many spawning pairs. If I were you, I'd go for no pairs if you want a community tank. I know you think your tank is "huge." But the footprint is just not big enough for that many pairs. Maybe start out with 1 male of each species you have listed, and get them all at about 3" size. That may work out pretty good.