Good luck with the electric fans. I know lots of people have good luck with them but I could never keep mine cool.
I started with my 340, factory 2 core, tried a single pusher, tried a puller, tried duals, always ran hot. Bought the same radiator as you but a 3 core same problem with electrich fans. Switched to a factory 5 blade and 325 shroud and Hayden hot rod fan clutch. Problem solved 180-200 degrees max. Dropped in a 408 and it cools the same. I broke a motor mount and shattered the shroud so for punishment I tried the duals again and to ran too hot. Ended up with a aluminium 325 shroud from wizard cooling and back down to normal temps.
hayden hotrod fan clutch - Google Search:
1970-73 22" Mopar Applications w/ OEM Style Shroud
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