I run an Optima in my Deuce. It's mounted on it's side, under the car, on the
frame rail. I got 3 years out of the last one. The current one is approaching
the 3 year mark.
I have a trickle charger that I move between my stored vehicles. Seems
to help.
Maybe you have a short somewhere? When you install the replacement
battery, watch for a slight "arch" when you attach the second cable.
The only reason I have the Optima, is because it can be mounted on it's
side, (the engine compartment on a 32 F&$d is very limited).