Looking to Buy 90 Gallon Long

We're beginning the planning process of finishing our basement, and step one is to find an aquarium that will be installed into a wall. Given the space that we have, a 90 gallon long would be about the largest we can fit. Something with around a 48x18 footprint. We could go a little longer, but not as wide as some of the standard 72" long tanks. 18" is about a wide as we can go because we need room to plumb in an existing 50 gallon system on the floor above.

 

We were thinking a 6' long tank initially, but we're putting it into the wall, underneath stairs, and I think it would be too tight of a fit at 6'. Unfortunately it doesn't seem like there is any standard 60" long tanks, otherwise that would be perfect.