I never found any kind of mark anywhere when I did my swap, and I did Scotchbrite everything so as to make any such marks visible.
There is a place near me in Arlington, WA called Perpetual Balance that I have have a few things balanced by. Most recently I had my flywheel match balanced. I skipped going through my machine shop and went directly to the balance shop, since no machining was needed. I can't remember now if it was $60 or $80 to get it done, but the owner knew exactly what I needed done, as he seems to do a few of them every year.
He does have a website at
Perpetual Balance | Your Engine Balancing Specialist Since 1985
No affiliation, just a satisfied customer.