Could it have been the black crud in the clutch bell that was smoking? Those old black clutch shoes are KNACKERED. Not sure two tanks should be able to do that to a set of shoes!
About the 1mm springs, yes Mugen make those and they should be available from the same place.
Been asking around and the Hyper 7 clutch nut will work (apparently). There have been several people telling me that they run exactly that set up.