I have done pretty much a complete work up on both 13B's and SBC's at 450HP. You really don't need more than the twin rotor at this power setting. At 450HP they are right at the limit for 91 octane pumpgas. Its gonna take about 15-17 pounds of boost, maybe a little more and in reality more than likely a blend of race gas and pumpgas. So the 13B's end up costing more than twice as much for the same power. The real cost is in the electronics and turbo/intercooler system. The other problem is a lack of GOOD used parts. The more I looked at them the more I could see I would need to pretty much build a new motor from new parts, many of them race parts, port it, run fuel injection and put quite a bit of boost on it. All this will require a stand alone engine management system and a lot of one off pieces. The cost really goes up quickly as you start building it on paper.
But I too have lusted after that sound, another problem in itself. These engines don't like much backpressure downstream from the turbo at that kind of power. And it would be very hard to get it down to the restricted sound levels required at some tracks. This and the cost is what has led me towards a Chevy as I plan my dream. "Fingers crossed"
But Fran is right, it would be cool in a Super Light track car. Maybe a lot better than cool!