Harrison was the factory supplier of radiators in the '60-'66 Chevy trucks and maybe other years, but I am not sure which ones. The large V8 radiator measures 25-1/2" wide x 22-1/2" tall x 3" wide and has HARRISON embossed on the top tank. It sits on the top flange of the radiator cross-member...the smaller six cylinder radiators sit on the lower flange of the radiator cross-member, between the frame rails.
To my knowledge, there are no model numbers embossed on the various radiators...I believe they are idendified by their top & bottom tank size, overall dimensions and number of cores. I did find the following part numbers and applications:
'63-'65 - (230)/Standard transmission Part#: 315560
'63-'66 - (283)/Standard transmission Part#: 3157071/3155062
'63-'66 - (292/327)/Standard transmission Part#: 3155105/3155061
'63-'66 - (230/292/283/327)/Automatic transmission Part#: 3155065
This information is pulled from the "Glenn Mitchell Collision Estimator Inc." "Part Number Service Guide", dated November 1, 1968, specific to the '63-'66 Pick-up, Cab, Panel & Suburban.
