Hy mystro, welcome, so you have a school bus to restore then? If you could look on the engine block for some raised numbers and post what you find here, that would help us to tell you what engine you have, this may involve a lot of scraping and wire brushing to find the casting numbers. The truck probably left the factory with a full pressure oiling system 235 engine, a 261 engine may have been an option for that size of truck in that year. A complete engine for transplant into the truck may be a better option than trying to resurrect the short block you have, hope that helps.
