I wouldn't waste the time, energy, or money on replacing gaskets before you start them up to see if they have any life left in them.
Drain the fluids into containers which you can visually check their condition (no water or ground up bits of metal in oil, no excessive rust in the coolant).
Add a few tablespoons of oil in each cylinder through the spark plug holes. Manually turn the engine over a few times to check for tight spots due to rust in the cylinders which had open valves while dormant. You can do all of this on an engine stand.
If there are no tight spots, turn the engine over with the starter with the spark plugs out and ignition off. You can do all of this with the engine sitting on an old tire or on a wooden stand.
If it turns over nicely, you can then get started on carburetor and ignition system.
