I have the same sorta dilemma and question in my mind. I have a replacement heater core that doesn't have a crimped inlet. This makes me wonder how much better my cooling system could have been if this wasn't bypassing so much coolant. Not really room to crimp it without getting into the hose retaining ridge. My solution is to install a valve. I'm converting to an LS engine. So my cooling needs should go down a lot. I'm installing one of these:
https://www.summitracing.com/parts/fss-84706 I may choose to close the heater core off entirely during the summer.