Houston, WE have lift off.
One part of your synopsis of the back story on your ride does make me itchy though. If your Cutlass did get "blessed" by Hurricane Harvey, however long ago, did you ever scope the inside of the frame rails or lift the carpet and check the floor pans, or pull the door cards and check inside the door shells? Water is one thing but Hurricanes have a bad habit of bringing along dirt and debris that they pick up and drop indiscriminately as they waddle along their random path of destruction. This is just me, thinking aloud here, but my tendency, presented with this vehicle, and Yes it does look in very decent shape externally, would be to treat it like a flood car and go OCD on the degree and depth that I dug into it in search of hidden grief or misery.
As for a choice of replacement mill, not sure what it would have come with as a stocker, but an LS swap, while fairly easy-peasty to accomplish, to me just removes a ride from the realm of both vintage and unique. and lumps it in with all the other converts. The LS mafia can hate on me if they want, but they can't deny that the LS generation of engines has become so common and prolific in numbers that about the only thing that hasn't come up for an LS swap is a baby buggy, and mostly because dropping the motor would take up most of the space for the baby, which sort of defeats the whole purpose of the swap!!! (Yeah, I know, someone on Youtube has a video of a baby carriage with an LS in it./ Go ahead and post it.........)
Although not so common, My vote goes to the Olds Big Blocks, 350 and bigger. Torque monsters and eye catching when you pop the hood on the unsuspecting audience.
All this aside, it is your ride, so have fun with it whatever you decide...................And Don't Forget the Pictures..............🙂
Nick