There are a few different Heads for the 350 Diesel..
All Heads will Fit on any year engine..depending.
Some engines had only ONE dowel pin on each side..not two..These heads also only had ONE alighnment hole..To use these Heads with most later engines, a machine shop would have to Drill a hole for the other dowel pin for the head to work.
The 78-80(early) Pencil Injector Heads..external EGR, These Heads are pretty tough to mix up with the other types..as they look different..they will match up to any year 350 diesel block if that is the setup you want..These motors had 125hp instead of 105. But where not as economic.
The late 80 heads introduced the newer Poppet Injectors which threaded into the head..It was an external EGR Head. Intake Manifolds can Interchange between 78-80 motors no matter what fuel system.
81-85 Heads..Internal EGR..These Heads brought a whole new intake manifold, which can not interchange with 78-80 motors...However, poppet injectors from late 80 motors work on the 81-85 engines.
Always Give your casting number to assure a direct fit.
If you find that your heads are cracked between the valves, its common..Heads crack mainly because of combustion temp. or overheating.. Cracks in the heads can usually be fixed at a good machine shop for a reasonable fee..I always run a cool thermostat in the motor in the hot weather and a Mid Temp in the winter and havent had further problems with Head Cracking...I have also heard that the heads on the Motors made in Canada do not crack but the Motors made in Mexico are the ones with the cracking heads..Due to weaker metals I'll guess..
How can you find a Canada Motor you ask? Youll have to see if the first figure on the VIN is a 2..You can also check the ID on the Motor for its Past..this is just something Ive heard however.
Always make sure the heads surfaces are True before Intallation...The surface condition of the mating surfaces play a very critical role in the 350 Diesel.