Loosing antifreeze

'79 Volare 225. When I got it , had a pinhole leak in radiator. Only drove it down the road and back, no distance. Did not run hot at all. I replaced the rad with a new one, thermostat, now it runs hot right away. No leaks, oil if full of water. Is this the head gasket or a crack. Anyway to tell without removing the head. Triple bypass and hernias makes me not want to lift that heavy sucker.
I was thinking of offering it for sale , as I really want an old hotrod. I have a good 318 to go in it, and easier for me to pull entire engines that move a slant head!! Thanks for the input.