I am picking up a 1967 blackface bassman head next week that will be used with a stepdown transformer as I'm in the UK. I intend to use a non-original cab with it and was wondering what ohms options I have? I believe the 2x12 bassman piggyback cabs ran at 4 ohms - can anyone confirm this? If this isn't the case, or there is a means of adjusting ohmage on the amp, I'd be really grateful for any advice. Thanks!!