Is there a simple/easy way to ID a 273 engine vs 318?

My 66 273 doesn't have "273" by the casting number but the casting number tells the story. This # is for 64-66 273 only. There was also a #2806130 for some 65's and up to 69 when 273 production ended. I don't see any LA 318's that share the same casting numbers.

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The '68-9 273's I've seen have the -273 after the casting number. As you mentioned, the earlier ones don't. Easy enough to look up though.