ZInDc

I'm about to buy a 1971 Series I 240Z out of state. It looks in great shape, but the mechanic looking at it can't find the engine numbers to confirm it's the original engine. He found the number on strut tower, but can't seem to find the number on the engine block. I had been told that the number is "where the block and the head meet near the trasnmission and on the passengers side," but my mechanic still can't seem to find it. Is the number somewhere else? Engraved on a plate or directly into the engine? Is it possibly obscured by something? Please provide as detailed a description as possible so I can help my mechanic find the number..... I'm really grateful for your expertise and hope you might be able to provide additional wisdom. ZInDC