Flowkooler water pump for 340 going into a 1964 plymouth valiant

FYI: on my 66 barracuda with the 273 and factory cast iron pump and factory radiator with factory fan shroud for AC. (I realize it is 100% different than your set up.) I got a factory style clutch fan to work. When I get to my shop today I can get the measurements. I used an 18” factory clutch fan from a Dakota with a four bolt flange. So I assume that it came from like a 96 style Dakota with the v8. 88 Jeep wrangler with a straight 6 I was told also fits. Very short mount shaft and the 18” fan blades clear the not so wide radiator and shroud of the early Abodies. Hope this helps you. Look up the specs. There are clutch fans out there that will work.
Syleng1