Help Identifying Model of this Old Euclid/Terrex Loader

We just bought this beauty (clearly we need to replace the motor the guy we bought it from has a replacement we got in the deal we just have to install it.)
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But we are trying to figure out exactly what year and model it is We know that the motor is a old Detroit Diesel 71v6 ( not sure if this one is turbocharged) and that it roughly is a Euclid or Terrex 72-21 or 72-31 we've been looking at other 72-21 and 31's but they don't seem to have a DD71V6 in them, they all have smaller engines so any help figuring out the Model of this beauty would be very helpful thanks.

Just shot Terex 72-51 .

Hard to tell as all the 72-21 through 72-51 look the same. I would guess from the engine and tires that it is a 72-31 or 72-41. The engine is a 6V53 ( you can just see one of the valve covers in the third pic, it bolts down around the edges, the 71 series had bolts in the center of the valve cover). I have a 72-41 with a 4-71, have been told that they just put whatever engine they had on hand in these, as I have seen several different engines in the same model. If I remember right there should be a serial number (& maybe model) stamped on the frame on the right side about half way up, behind the loader mount. Hope some of that helps.