The groove for the rear rope type main seal is built into the Oil Pan. Not I have never removed the Oil pan but I believe I read in the Manual that there is some sort of centering tool to center the front of the pan to the crank shaft so that the seal bore is lined up. However, I don't know how necessary that tool is.

It depends on if you want to change the Rear Main and front Crank Seal or not before you install the Engine.

If the only difference on the CA Oil Pan is the lack of the blow-by oil drain you can take care of that with a different blow-by setup. Does it look as if the Rear Main Seal on the CA Engine was leaking?

Personally I would only use what is in the old car with the bad Engine and don't use any of the specifically CA stuff.

You did not say which transmission you plan to use. The CA has a different vacuum system and slightly different transmission. I am guessing if you use the CA Transmission you are best off with the CA vacuum system.

I don't know if the 83 has the EGR or not. If so if you want to you can plug off the EGR if you have no State Inspections to pass.

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84 300D, 82 Volvo 244Gl Diesel