70duster 360 gets hotter the faster i go

I do too. Here's something "I always post" because this happened to me. OLDMANMOPAR used to be on here posted that he thinks that "use" thermal cycling, expansion, contraction, CAN eventually break the bonds between the rad tubes and the fins.

I saw this on at least one rad shop tech page, also.

I had my original 67 rad, allowed my 360 to run hot at speed, even though a shop told me it should "be enough."

One week I threw a later /6 rad in the car--same 2 core except newer tanks off a 73. INSTANTLY the temp gauge dropped a sizeable amount, and the engine ran noticeably cooler.

WHAT IS NEEDED in the auto industry is a legitimate, repeatable, test setup to equate rad heat exchange, IE a set water flow, airflow, and BTU exchange.