[ElmoPerkins]

I just went through this with my m42. Mine had a cracked coolant passage. I was lucky and sourced a used one with no visual cracks and all threads where in good condition. It’s was mostly disassembled so finished removing everything and sent it off to a local machine shop and have it glass bead blasted, cleaned and checked over for issues. Head was flat and guides where good. It maybe a gamble going used, but as long as the engine ran with no problems prior to removal, it should be ok. I went ahead and replaced valve guide seals and lapped the valves during reassembly myself to save money. Hope this example helps.