I have an Optima orange top in my 124, so they do exist. It was a perfect replacement for the massive stock battery. It's the same width as the stock battery so fits in the tray and hold down perfectly, though it's shorter and a small bit taller. Battery cable reach is no problem with the reversed terminals.
I'll point out that no standard car battery is a deep cycle battery. They are all designed to deliver a large amount of power for a short period of time. My wife killed the three year old Diehard in our 124 wagon earlier this fall by leaving the headlights on for a few hours. The car would barely take a jumpstart and would never restart. That's what I call dead.