Identifying what year on a D24
 

I found a 1980 240 diesel at my local junkyard. I know that the head bolts on the 1980s are smaller than the other D24 240s. Today I looked at the head bolts from the motor it looks like there are the same size as my 83 D24 I have in my shop. This meaning maybe a later D24 swap was done on that 1980 Volvo. My question is there any markings on the block/head that would tell me that it's a 1980 D24 or maybe a different year.

The bolts are switched. Many did that. My father has done it very many times on 1979-1980 diesel volvos. If you are lucky is the engine overhauled.