There are two different 235s, pre 1953/54 and post 54. Pre is low pressure, which relies on dippers and splashing to keep it interally lubricated. Post is higher pressure and lubes better, which is particularly important with high revolutions.
Another difference is the rod bearings. The 216 has babbited rods- that means the bearing is basically part of the rod. More modern engines have 'insert bearings', which are easily replaceable. You might not have a choice but to have your rods machined for insert bearings or flat out have to replace them, if you rebuild the 216.
One possibility, to keep the original appearance but improve performance, is to switch to a 261.
