Les,
I am not sure who made the radiator surge tank on the 2003 Thunder. The Ford surge tank that you are referring to was used on SMC designed Beavers with 2002 being the last one. However you can call Beaver Coach Sales in Bend, and they will tell you who Monaco bought the surge tank from. Some of the Monaco era coaches did not use off of the self surge tanks so you can only get them from a Monaco dealer.
Gerald
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