I’m no expert but all that is usually done is join the pipe from the modine that runs around the back of the engine and usually goes to the heater matrix, and then just join it to the stainless tube that runs to the water pump which then goes on to go through the radiator, I’m sure Rose motorsport used to do a hose for this!

You might have another issue if it’s over heating at idle, as I have done this in the past as a temporary fix when my heater matrix was leaking and had no issues whatsoever.