If it's a V series engine... then I don't think it's original. I do not believe they ever used the V series in the x55 tractors. The engines that JD used were 3TN84RJ which I believe were of the E series. Not to say that the V wouldn't work... it's basically just an updated version of the same engine and I'm sure it would bolt right in. Just trying to help clarify to help in your search for a replacement block. I don't know how deep your pockets are, but a brand new short block can be had from Yanmar for about $3,200. I just got done rebuilding a 3TNE88 for my 955.