Water pump rotation in a big block housing?

No clue on the impeller blades. Would probably work, but slightly less efficient. I wouldn't use either cast-iron water pump housing. You can get an aluminum housing and pump ~$120 on ebay. I may swap to that on my 65 Newport to take 25 lb off the front end.

Shop around for radiators. I recently got a new aluminum Pro-Cool one on ebay for $80. Was thinking of using in my 65 Dart, but would have had to cut off the frame rail lips to fit. I put in my Newport (w/ shorter battery tray). Has no trans cooler, but I prefer a separate cooler anyway to avoid water in the tranny. The original round-top radiator in my early Mopars tend to split at the upper seam. Yours is the better square-top. You could probably get it rodded for <$100.