It's a well painted mutt... I would say from looking at it... it started life as a 3600 conversion built from a very basic skid. There is no hydraulics but it does use the single reduction rear end... suggesting it was a 3600 skid. Note the lack of differential lock pedal that would also have been present on all double reduction rear ends.
Add to that... the shif decals suggest it has the 6x4 manual reversing transmission.
The engine is a 10 series engine given that the block has external ribbing. That's not really a big thing given the number that pinholed over the years. Many just dropped a BSD engine in place of the bad engine... or at least changed out the block to the new style on rebuilding. The rest of it... sheet metal and all... looks to me like a 3600. It is quite possible that the engine was upgraded to a BSD332 or 333 that would make the suggested 55 hp...