If owning and doing is doing, then you loose. Been there done that with more than one SB-220. Without a change in primary transformer you'll never see enough plate voltage to get 3000 watts, I don't care what you drive it with. Without substituting a 'Peter Dawhl/Dahwl(sp)' transformer that won't fit into the SB-220 if you removed the tubes and RF section, forget that higher plate voltage. The standard 'HeathKit' transformer was barely adequate to start with. You can also plan on rebuilding the rectifier board, metering circuits, and find a couple of chimneys and a blower. The standard fan won't come close to being adequate, it barely is with a stock SB-220. I think I may still have a filament transformer around here somewhere, the rest of that junk hit the road a long time ago.
The SB-220 was a pretty good 'almost legal limit' amplifier in it's day. It certainly wasn't/isn't as 'fantabulistic' as people try to make it sound like. Take a look at Rick Measure's web site. He comes closer than anyone else with most SB-220 mods. See what he has to say, then wonder about that 'talking' and 'walking' thingy...
- 'Doc