sf power 3 mono

please help , need some info on retube these amps, what
is the best tube for these amp. my speaker is 4 ohm.
and want to buy original manual for these.
Last I heard, SF's folks were recommending Svetlana 6550's, which is what I use in my 160 mono's. This is an excellent new production tube. If you buy these be sure you get the ones made in St Petersburg. Svetlana has sold its name recently.
thank you Newbee