dude, you must be crazy! If you're really going to swap an engine than my best recommendation is to get a complete rebuilt rotary turbo engine ... a good rebuilt race spec FD engine will do. In USA they have a rx8 drag car running with a 20b 3 rotor turbo engine. Please dun put a piston engine into the rx8, it practicaly will screw everything up and you might end up with something WORST than b4!
And just a small correction;
The Mazda rotary that entered the Le Mans is a 4rotor, not 3 rotor :)
The mazda 4 rotor car was SO-SO fast that NOBODY could even come close to them, not even the V8 vipers. Aparently they are always so far ahead in the race (like 6 - 7 laps ahead) that they had time to stop the car in the pit stop to wash the car so that it will look good when it crosses the finishing line and still win 1st place! I'm serious!! I got this info from one of their ex-pit crew while i was in Australia.
Aparently also that because they kept winning without a fight, every other car makes started complaining and finally the Mazda 4 rotor car was banned from the Le Mans race and the car was placed in a Muzium!