I would have built a cool motor like yours. I wanted an easy to obtain motor to simplify what is otherwise quite a laundry list of options on my turnkey. The external balance, heavy crank, and other things you mention, are negatives for the 514,..BUT.... it was convenient for my first motor in my turnkey. I can hope.
If and when the 514 bites the dust, I will likely have some good shop make me something like yours. The higher top RPM is perhaps the most appealing...wider powerband I suspect.
Oh, one thing: The 514 (like mine) has Eagle rods now, and ARP bolts.
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