Average price of a 20B rotary engine?

I have 1987 Mazda RX-7 Turbo II and as of right now it has that repulsive S4 turbo engine in it. Don't get me wrong, I love RX-7s and rotary engines but that particular setup is the worst ever. Inconvenient and difficult to work on. A 20B would be PERFECT for this car and from what I've heard they bolt right n. I just wanna know how much a descent one would set me back. Including wiring and ECU modifications. Thanks!