Need help identifying NH diesel

[SoonerLS]

My dad has a '65 4000 with a mid-'90s NH Industrial diesel, and we're trying to figure out which engine it is so we can order the parts to overhaul it. (It has bad blowby--it smokes like a destroyer escort at Leyte Gulf, so we know it needs rings at the very least.) He bought the mill from a NH dealer in the late-'90s (it had 200 hours on it, and cost about the same as overhauling the original gas mill), and he thinks the dealer told him it was from a NH 540, but the only thing he knows for sure is that it's a Ford/New Holland Industrial 3-cyl diesel.

If someone could point us in the right direction on accurately ID'ing this mill so we can get the right parts, I would appreciate it.

 

[DT86]

We can guess all day unless some one here is familiar with these conversions. Isn't there any numbers cast on the block?

 

[SoonerLS]

Yep, should've included the casting numbers;
Left side of the block:
HG2 4A20 (could be 4A2O)
There's an A B C D circle with an arrow pointing at the B
There's also a "BB" lower down, ahead of the New Holland logo

Right side on the intake:
05NN 8425J