We were there last spring, the ranger just barely allowed us to go through. They have markings on the pavement at exactly 50'. we are about 50'9". He cautioned us more about the switchbacks, than the tunnel regarding length.
Made it through fine and took our time on the switchbacks. Since we were first in fairly long line, I pulled over after the tunnel to let the other vehicles pass before heading down.
I would guess since you are at 36' with a toad, you will be too long unless you unhook and have someone else drive the car. Regardless, enjoy your visit the area is beautiful.