Everything that bolts to the rear of that 216 will fit the 235. Be sure to use the 216 flywheel if you are using the 216's starter. It will work well with 6 or 12 volts. The 12v starter needs the 12v flywheel.
You will be faced with the decision of what to do about the waterpump. The preferred method is to get one of Dave68's conversion plates on this site and rebuild your 216 waterpump. The 235 pump is too low to center with the radiator and the fan will hit the radiator. That method is a can of worms to make it work satisfactorily.
