Someone mentioned the 323 GTX Turbo. The B6T engine in this car is shared with the late 80s-early 90s Mercury Capri XR2, and I believe could be a drop-in replacement for the Miata provided you have the bellhousing and ECU.
But yeah, if you're not a "wrencher" (I'm not one either), I agree a decent used engine is worth considering.
