Abandoned 1974 Camaro

I stupidly abandoned my 1974 Camaro LT L-48 4-speed nine years ago with a full tank of gas. It has around 118,000 original miles. The 350 engine was rebuilt at 93,000 and the clutch was replaced just before I left it parked in an open, but covered shed. Even though I don’t deserve it, I’d like to get it going again, but afraid the engine is likely frozen. What would be the best solvent to pour in through the spark plug holes to free up the rings?

One step at a time. Don’t start with solvents. Use motor oil and try to turn it over by hand. Work with it for a few days id needed before doing anything more drastic.

BTW I would drain out all the old gas.

I have found that tranny fluid works well for this as well. I second draining the gas tank and replacing with fresh fuel. Also replace the fuel filter and new spark plugs.

New hoses, too.

It sounds like you’re not sure if the engine is frozen or not. If it is, then I would pull the spark plugs, squirt in some trans fluid as Dartman suggests, and allow it to soak for a couple of days.

Use a long breakover with a socket and try rocking the crank pulley bolt back and forth.
Ideally, once the engine is free (and even if it is not frozen up) I would suggest removing the distributor and using a drill to rotate the oil pump shaft. This will provide oil all through the engine before startup and you will notice it by the drill bogging down as pressure builds.

As mentioned, you will need to replace belts, hoses, and tires also.
It might not be a bad car to hang onto as the second generation Camaros are starting to appreciate in value.
Fifteen years ago they were near worthless and now, due to many of them being beaten into the asphalt and converted into race cars, the price is climbing on them.