If you want to compare apples and apples, how about the GSIO-720-A1A
at 520 HP?
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I have to assume you are pulling my leg...... (maybe not?)

From my understanding of the Lycoming model numbering system it
wouldn't seem to have any torsional dampers. There have been some real
nightmare engines in Lycoming's past - like the dual crank H
configurations etc. Their archives would be interesting to peer thru.