Sorry to hear about your accident.
Your back has healed before.... Doctors are never right, an old mates father was meant to be dead in 2000, he is still here...
If anything, I would go different seats, change the suspension, and clutch that is smooth to engage. My stagea is hardly stiff to sit in(my 82grandmother with a damaged spine finds it fine), but handles more than well enough to keep me very happy. A Stagea that looks good, has power, is comfy and set up as a cruiser is still a nice car! Yours is only a suspension and seat change away from this.
The car is a tribute to your father, you have been thrown a curve ball, medicine is not an exact science, and our visions for our cars evolve/change with our lives.
Look at all the natural therapies aswell as what the doc says, and take care of yourself. It won't kill the car to sit still for a year while your back stabilizes, and might save you from a decision you will regret.
-Ryan