A couple of guys in FFCC have done that install (including Wozzah!)
One with quad throttle bodies claims around 230hp and is faster than his old worked Pinto on 48's....
It is a BP rather than a B6, but the 1800 is quite common and cheap if from a Laser (under $100 an engine compared to the same from an MX5 at $500+ each), but you do need a number of MX5 specific parts like gearbox, sump, waterpump etc to install in an Escort N-S style....
Bonus is it is light and even looks a little like a BDA...