Engine casting number is 3040912R4 but maybe the first digit is a 5.
That serial number plate was on the right hand side of the tractor. Clutch housing I think. I thought the 3 point hitch was Cat II, but now I'm not so sure. The implement end is Cat II, but the other end, where it attaches to the bottom/back of the tractor appears to be Cat I.
RE: Research
I've been poking around on the web, googling around, and haven't matched anything up either.