I own a '77 300D and replaced my old OE radiator with one made by Performance Products (at the time it was called Impco & located in Houston, PP bought them out). I bought the aftermarket non-OE radiator that is all brass instead of the Behr brand that has the aluminum core with plastic tanks OE type for $100 less than the OE (bought about 3 years ago). The brass radiator has performed as well as the OE and has a 24 month transferable warranty. PP sells both types for your 300D: Behr OE type for $313.30 and aftermarket for $225. PP phone # 800-243-1220.
America: Land of the Free!
1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.