kt 66

Hi all, IV been offered a mid 70s valve hd.. it was made in Oz or NZ (not sure).. Anyway, please excuse my ignorance but it's running 2 KT 66 output valves, and guy records output is rated at 120watts... I know commonly 2 xKT 88 s will easily rate 100.. Anyone have an idea if 2x 66s could...