I have an original '57 standard bore 312 block that I managed to strip out the threads in one of the mains by using the short bole 49 years ago. Cobbled up a longer bolt in the stripped hole and ran it for while with no problems. I am cleaning out one of my storage garages and need to know if this can safely be repaired or should I scrap it? I have a couple of spare 292 blocks that could be converted to 312's but I hate to trash something that I may need or someone else may need.