Fixed cooling fans for a 340

I’m going to throw in my personal experience. My 1972 Duster has a factory 22” HD radiator (the standard radiator for slant 6 with air conditioning or a 340) and has been swapped to a 340 from a slant 6 before I bought it. It was cooling fine with a fixed 7 blade fan, but I was not impressed. On a 80 degree day in the direct sun it would not overheat, but it would not drop back down to 180 very fast until it got in some shade. As I researched the fan specs, what I found is it was utilizing a 7 blade 17” fan with 1.5” pitch, factory correct for slant 6 with air conditioning. So somehow the car had gone from its factory slant 6 with AC configuration to a 318, and then to a 340 all before I bought it and everyone kept the slant 6 fan… lol. The factory correct fan for a 340 is a 215 clutch fan with specs of 7 blade 18” with 2.25” pitch, also known as factory Hemi fan… so overpriced. However, I found that the GM 772 fan is reproduced and costs about $130, bolts to the same fan clutch a 215 would, and has the same specs of 7 blade 18” with 2.25” pitch. The bonus is the ends of the blades have the turned up ends which supposedly makes them cool better than straight blades. Anyway, I bolted a GM 772 fan onto my 340 and on a 90 degree day in the direct sun with spirited driving, it maintains 180 and gets back there quickly as needed, such as on restart after heat soaking. You have a shroud and your fan relationship appears correct, you just need more pitch. I would recommend trying the GM 772 fan first, I am very satisfied with mine.