1971 Demon with some coolant issues

I am near Spokane, Washington..

Right now I am leaning towards the 360/380 Magnum. The best price I have found on those so far is Summit Racing (unless someone knows somewhere else). I looked at some remanufactured engines, but by the time I get it to where I want it I might as well just buy the Mopar cate engine.

I am not familiar with the drivettrain on my 71 demon, it has a column shift Auto trans, original engine was a 318.. not sure what rear axle I have. Will my stock drivetrain stand up to a 380hp crate engine?