Apparently there is one for sale in WA
state, with 74 hours SMOH, on this site, no price listed;
Additionally, Covington Aircraft Radial Engine Division of Covington Aviation rebuilds R-1340s, I assume you need to have one that needs to be rebuilt and send it to them. But, they may also sell newly rebuilt engines. My guess would be around $40,000 plus shipping.
Sorry, that is the best I can do, as I don't have a spare R-1340 hanging around my house.