How big of a tank do I need?

I am currently in the planning stages of building my own plywood tank that is 300+ gallons, and am wanting some advice on how big I should make the tank, based on what will be going into it. Because of the space I have to fill I am thinking of a footprint something like 72-78"x 36-48". Below are the fish I have (or will have) in my growing out in my various smaller tanks, and if there is a size listed next to them, that is the size they currently are. If there are any on the list who really wont work together I can probably work it out so that they can stay in their current tank, or a smaller, big tank. I just would like to let as many as possible of the big fish be in the big tank!

1 Astronotus crassipinnis (smaller cousin of the Oscar -3in)
1 Pair Vieja synspilum (6in+)
1 female Carpintus (getting soon - 3in)??
5 Satanaperca Leucosticta (1in)
4 Orangespot Acaras (1-2in)??
5 Geophagus Altifrons
1 Pair Uaru
1 Hoplarchus psittacus
1 Heros Notatus
1 Paratiliapia Bleekeri
2-5 Paretroplus maculatus
1 Fire eel
School of pictus catfish??

I haven't fully figured it out, and I am planning on getting the materials bit by bit, but I think the two main cost are the epoxy sealer, (if you use that method, but I plan on using pond liner, which is cheaper, and a can disassemble if need be) and the glass for the viewing pane, but I am trying to find someone with a big, busted tank to recycle some of the "unbusted" glass. I am probably not the best person to ask, since I haven't actually built it yet!

Yeah, the space I have to fill up (I would kind of be creating a wall) is 81"x40" It is and odd size but I think it's be a good footprint. It's more space than my bantam chickens have in their coop!

Probably a big sump packed with bioballs, lava rock, and filter media. Plus pothos, and maybe an aquaponic bed.