You are correct. There are some interchange, but not all is right with the required application. I will ckeck the 55 cast iron bell in the morning. It was an option for the 350 small block. It mounted up to the frame via kit mount. The 55 bell mounted to the '49 4 speed. For ten years, the project was idle. My solution was to bring the 216 back to life. I have done some modification in the past, but that is in the past. For the 350 to set in, the heart of the firewall was cut out for the HEI. That alteration has been resolved. The 216 is in the engine compartment and the 3/4 will make it's debut mid Jan from the paint shop. I will get the specs on the 55 bell in the morning.