I know
@Craig has notes on grates, even down to the shapes of the bends on the handles. He's obsessed.
I don't know if the data was consistent enough to warrant a guide though.
For 22" kettles, I always go with new grates. The vintage grates were thicker, but I've never found one worth restoring/using.
For the 26" grills, the new grates don't fit the old grills