Not sure where you're getting your info, but a standard 150 is 72" long (6ft), so the total dimensions are 72x18x24 (LxWxH). It's the same as a STANDARD 125 gallon, but taller.
You're correct, my bad. I was rushing and posted. The 125 is 22" high, 135 is 24" high and 150 is 28" high. They're all the exact same footprint, just get higher as the gallons go up. I guess the OP can measure the height, so you'll know exactly how many gallons you're getting, but the footprint is the same, so they'll work in whatever space you have for one or the other.