16 years. Wow. Solvent could take a lot of the gum out but it might end up being a combination of rust and gum in the tank. Not knowing how the car was stored I'd figure as a minimum take the plugs out paying attention to their condition for rust and what not. Then if no rust on any plugs you are very lucky. Also as a minimum take the valve covers off and look for rust. If no rust then you should make a trip to Vegas being on a roll like that. If no rust under the valve covers and plugs I'd try redoing the oils, coolant, and other fluids. Make sure everything is tight then prime and flush with a super light oil to see what comes out and then go to 10W-30W or just 30W for a quick few minutes of running. Not sure of the weights actually. Whatever oil you end up using for running the engine I'd change it not long after with the filter.
Your brake lines, calipers and cylinder will probably have water in them from the silicone pulling in moisture. It normally has rust in the lines, master, calipers and cylinders. One good thing a complete brake job is easy.
I hope you don't have to tear it down but rebuilding it might be the best answer. The gaskets right now not knowing what a running engine is might give you trouble.