340 coolant in oil

Check and see if you have any plugs that appear to be steam cleaned on the left hand cylinder bank, you may have pulled the wrong head. Has it been losing coolant or have air bubbles/positive pressure in radiator, and do you have a bulk of water when you drain oil? Any overheating? I still would have the head you pulled magnafluxed, though. A compression test before teardown may have helped, and you may be able to run one on the left bank, but you'd want to temporarily plug the rocker oil supply on the right deck before running one as well as catchwhat comes from the fuel pump. Set up a jumper wire with push button switch to the prong on solednoid with yellow wire, this will let you crank over with starter without the ignition turned on.. having the valve seats and guides checked on the head you pulled may be in order as well. It's entirely possible that if it's just a little sludge with no coolant loss it could be condensation, but only if you live in a high humidity area. Is the underside of the gasket intact as well?