7 blade 17” fixed fan vs 6 blade 18” clutch fan

68 340 came with a 213 fixed 7 blade fan stock unless it had air conditioning. That fan is a 1.75 inch pitch. In 69 they went to a 214 or 215 7 blade clutch fan. Can’t recall the part number, its one of the two. That fan is a 2.25 inch pitch. That is pretty much the same as the 216 mopar performance fan. Best to stick with parts as mother mopar engineered. You can find the information in the parts manuals.