Undecided need some input for new tank?

[Marlin65]

I want to take down my 75 gal cube and build a room divider. My ideal tank would be 6' long by 24" wide and 20" high. I would like a close loop on a Dart as I would take those parts from my 75 cube.
I also have a big tank one floor above so was thinking of plumbing them both together. To make a bigger water volume. Not too sure if that's such a great idea. I would think that will take a big pump.
The glass to put this together will be reasonable for me as I work with glass.
That or I can just buy a ready made tank. but most are not 24" wide or tempered. I like tempered stronger and it has flex. I was also thinking of doing the drop down L tank but think I might do that with rocks or adding some glass as I am paying for all the glass anyway.
I am not sure what way to go right now but if anyone has a tank close to that that they want to get rid send me a pm.
Looking for some input as there is lots of people here that have great ideas.