The best things about the RX series is that they were originally rotary engined cars. So your muscle car recipe is half there.
Get hold of a 13B-REW and you are in business, little fiddling to fit, and the rest is perfect. If the 13B is out of reach, ask around with some really oldschool junkyard guys, they will point you correctly to sourcing a 12A rotary from the FB RX7.
The cars look beautiful and with rotary engines, sound like nothing on earth.