You could probably mount a couple of Penguins on an Elco like boat, but mounting them on an actual 80ft Elco would be a waste of money.
By the time you could get missiles on them (About 1979 or so) they would be at least 25 years old, which is at least 15 years more than they were designed for, if not more. Their highly stressed wooden hulls required continuous upkeep by specially trained workers and a steady supply of surprisingly expensive building materials. (Layered mahogany of the required strength is surprisingly hard to manufacture)
On top of that the boats were cramped even by 1940ies standards.
But the real killer is their power plant. These boats were powered by three Packard gasoline engines (Which have a tremendous sound btw) To give you an idea how dangerous gasoline is on a naval craft you should check out the loss statistics for the PT boats. Of the 99 boats that were lost during the war, somewhere between a fifth and a fourth went down due to gasoline explosions, and that doesn't include the ones caused by enemy action.
And lastly, while they have plenty of power for going forward, they are severely underpowered when it comes to electrical generating capability. As a result you're unlikely to be able to mount the computers and radars required to turn her into an effective combatant.
For a comparison, take a look at the much more sturdy built and diesel powered E-boats of the Kriegsmarine. Even the most stubborn ones were long gone by 1965 and their value had been questionable for at least a couple of years by then.
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