Try putting air pressure into the cylinders with the crankshaft locked- - - -put the transmission in high gear and chock the wheels front and rear and/or set the parking brake to keep the vehicle from moving after turning the engine so the distributor rotor points toward the spark plug wire of the cylinder you're testing. Make an adapter from a discarded spark plug shell and an air hose quick connect fitting. I use an air pressure regulator to put 20-30 pounds of pressure into each cylinder. When you find the cylinder with the leak you'll see bubbles in the radiator. It's also possible to splice the upper and lower radiator hoses together, bypass the radiator, and pressure check the engine block and cylinder head that way. Don't forget to isolate the heater core to prevent damaging it.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!