The Rotrex blowers are rather small European superchargers, they are not designed for big engines, which is why you need two of them, they are great superchargers.
http://www.rotrex.com/
Tom what is the weight of that mounting plate? It looks like 1 inch billet, I'm just curious how the weight of one of these engines would compare to a similar hp twin turbo engine. I'm assuming that you ran it with a intercooler, so all of the charge piping and intercooler probably weighs the same as a tt setup.