Glad I stumbled on this one. Nihms, was the fully dressed, with pulleys, the version you got?
I think the path of least resistance is a new radiator. You will want good cooling anyways for the new Power plant. 1970 + radiators do have the outlet on the passenger side, and different timing cover that your original engine had.
Regardless I think the right answer opposed to buying a "1970 radiator" is to call a reputable company (I prefer griffin) that can make one specific to your needs, and will be a direct bolt in.
I don't know if you went with something more like a champion, if say a 71 radiator would need the mounting bracket, or holes, modified. I imagine any A body radiator can be made to fit, but I can't speak to if earlier cudas have the same core support holes, etc. Or if something like factory AC made anything weird.
Lands me back to calling a company like griffin that will have those answers, AND get you an awesome unit that will cool that monster excellent!
My griffin equipped dart with 600+ hp, I street drive, and barely even turn the fan on.
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