What's your plan to deal with the remains of 20-year old gas - tank, lines, pump, carb? If that's solved for sure, then proceed...
Pull the spark plugs and fog the cylinders with WD40 or Marvel's Mystery Oil. Take the crank pulley off, put the bolts back in and bar (rotate by hand) the engine a few times around. Mark where the distributor rotor points, then pull the distributor. Borrow or buy a prelube rod. Take the valve covers off. With fresh oil in the pan and a new filter, chuck the rod in a power drill, insert it down the distributor hole into the oil pump shaft's slot, and spin the pump (clockwise) until you draw oil up into the engine and it starts to come out of the lifter rods / rocker arms. Now you're primed. Put the distributor back in, and make sure the rotor matches where it was before. May have to lift and realign the gear a tooth one way or the other.
If the motor turns freely, the radiator is holding coolant, and it's got fuel in the carb, try lighting it up.