Valve change to KT120

I just have a Sansui BA303 vintage valve power amplifier and come with the GEC KT88, sound great. Now I want to change the valve to KT120 to find out what sound difference bewteen KT88 and KT120, but I worry about KT120 will burn the transistor , capacitor ( information from the web) or cause the minor damage of the amp after the valve change. Any expert advise I needed before I take action.

Thanks
Derek