Glad to see you got it figured out. You'll want to take care of the rust issue. Some recommend Kreme or POR-15 to strip down the inside of the tank and seal it. Others have been using Evaporust. I have no exposure to any of these methods. I DO recommend getting an inline fuel filter between the petcock and the fuel manifold for the carbs. Something like
this one from NAPA, perhaps. Don't forget the petcock: if there's rust in the tank, there's rust in the petcock too.
One more thing: this is an all volunteer group here. Most of the people here have other things going on in their lives, and may not get back to you as quickly as one expects.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.