Yeah, Burandt worked with Boondocker on the RTR concept. They wanted to sell them as turn-key sleds with turbos and a bunch of aftermarket, basically what Burandt rode when he was on Cat. But it doesn't come from the factory like that, Boondocker just bought stock M8s and put the stuff on.
The HCR is an Arctic Cat production model, and is what Arctic Cat's supported pro hillclimbers use. No turbo. The suspension is better for big bumps, track is better suited for firm snow conditions. The M8 Sno Pro is probably the better mountain sled for dry powder snow.