There are only small differences putting the early 235 in for a 216. Throttle linkage pivot point, and thermostat sending unit size are two that I can recall. There is an adapter for the sending unit, and for the throttle linkage it is best if you get what was on the 235. The fan is different, you will need the one from the 235, your 216 fan shouldn't work if it's original. Patrick's catalog has an article on the swap, see the links page. For the later 235, the only major problem is the lower water pump, a short shaft pump is needed.
