The big difference is the rod bearings. The newer 235 has steel backed insert style bearings. The 216/early 235 have poured babbit rods. Since the poured babbit bearing is thicker, it is easily displaced under load, resulting in stretched rods. This can be remedied by getting the rods machined to accept the insert style bearing. Due to the stretching, the 216 can not endure coninuous operation at higher rpm.
