I have 2 chevy fan blades available to use on a 235 engine with the short shaft w/pump. One is off of a 216 (18" dia) and the other I got at Hershey for $4 (17" dia) and I don't know what it is off of (not sure anyways - could be a 283). What is the proper diameter of a 235 blade? Any way of positively identifying it? As always Thanks for wisdom.