How did you mount the engine/transmission?
I am surprised that your 350 mechanical fan isn't close enough to the center of the radiator.
I had no issue with the '49 and the '52 that I put 350 engines in. I did use serpentine belt setups from a junkyard. I had to choose the correct fan spacer to get my flex fan close enough to the radiator. Both of them run right at 180 degrees all day long. 190 with the A/C on in 90+ degree weather.


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission