Jarcher, I'm afraid the above posters gave you some bad information. Atomic 4's are always subject to debate. especially by those who have never owned one. A late model (post 1970) A-4 in running condition goes for around $1500. Rebuilt ones are higher. My 1976 model served me well for 20 years. I had it rebuilt in 2001 and it still runs strong to this day. These engines are pretty simple, low compression, and designed for a marine environment. The direct drive models have a reversing gear for a transmission which is built like a tank.
Some would have you believe that these engines are dangerous. Simple precautions that every power boater routinely takes with an inboard gas engine are pretty easy to do.
My advice- look for a running take out of an A-4 from the Great Lakes. Buy a rebuilt carb as a spare (easy to install) and you are good to go. Change the gas filter annually and the oil at the end of the season and the beginning of the season and the engine will last for a long time. Of course you can repower with a Beta diesel for 8-9,000 installed which is a large part of the boat cost of a Cal 29. Or electric- just don't take any long trips. These guys are all nuts who really don't understand the economics of owning an old sailboat.