The LS3 is a massive lump:
https://www.ebay.co.uk/i/223785216487
I don't see this ending well, my predictition is that the bottom will fall out the market for this type of vehicle. This is as they say, the last bounce of a dead cat. No way 400+hp conversions are going to be either on-message (climate change) or socially acceptable and expect some form of massive tax hike in any "developed" country. I'm expecting the same for all those 500hp Merc AMGs - running costs on those are already over £2.50 / mile. Those of us were around for the first oil crisis watched tastes change very fast. 40years on and the big engines came back, but I don't that in 40 years time, it will be electric.
These things will drag on for a while in 3rd world countries that aspire to be first world but don't get it (think Saudi etc).