I am currently experiencing head problems with my 3T engine. I am about to fit a recon head which I purchased but they are becoming a rarity in Australia to the front two cylinders which the previous owner had also replaced but the engine was still experiencing blow back into the radiator from the rear head. I recently filled the radiator with cool water after the temp was up and now am getting water in number two cylinder on the front head which is why I'm replacing it. I am also trying to source another head for the rear cylinders which means I will have three heads spare but leak. Can these heads be welded or are there are other things I can check on the heads for leakage before they go to the scrap bin.
Try putting this question in the "dozer" section.
Have you checked all the precombustion chambers are tight and have good seal rings at the bottom? Much more likely trouble spot than a cracked head I should think.