The LS6 shouldn't be covered by cheap plastics, so I removed the plastic valve covers. This only revealed a new layer of connectors and sheet metal brackets, this is clearly not an engine designed to be put on display.
I replaced the sheet metal brackets with ICT billet ignition coil brackets, which helped somewhat (I also have to do something with the coil pack connectors). In hindsight, valve covers with integrated coil posts would have been even better.