Replacing metal coolant pipe for heater/tranny cooler (Type-44)

[Ameer Antar]

I'm looking for some advice about replacing the metal coolant pipe from the block to the heater and tranny cooler that sits on the side of the block. I think mine is toast and grinding it makes the holes bigger. I was thinking of replacing it w/ copper pipe and some fittings, but I worry about interaction between copper and the rest of the system which already mixes aluminum and cast iron passages. Anyone ever found a cheap alternative? Is it a lot from the dealer? TIA.

-Ameer