This motor I have with loop glow plugs and a 1978 casting number on the head has a delco r-4 mounted down low. It must have been the first year or some odd ball. I guess someone could also have swapped an older head on it, but it doesn't appear its ever been apart.
I hope I have found a solution. I picked up a 1982 motor today that was pulled from a pull a part by my neighbor in 2013. It is missing its injection pump, but turns over and doesn't look too worn from looking down the oil fill hole on the valve cover.
I will adjust the valves and do a compression test on it before making any decisions, but it is a carbon copy of what I pulled out of the car, so hopefully it is in decent shape.
It doesn't hurt anything to turn the motor without an ip on it does it?

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660