A couple of thoughts.
1. are you sure the head and the block match? holes all line up etc? Is it possible that you have parts of two different engines that are not totally compatible? 2. are you sure you have the right head gasket? Is it possible to put it on backwards or upside down? Sometimes holes don't line up if that happens. It did not happen to me but I know it can be done on a 3.0 Toyota engine and causes disastrous overheating if the engine runs for very long. 3. are all of the head studs straight? If not, uneven torque might result. 4. You mention the dowel pins. If you have any doubts about them, change them out for new ones. If you are certain of all of the basic things, then I would think you should have a good machine shop surface the block and the head to make sure that all is well. I assume that you are trying to build a very reliable powerplant to permit you to operate during times of grid failure. You need to be fairly sure it will be up to the task. Randy
