Dropping in a 5.0L Ford was common, and Ford's newer OHC 'modular' V8 is too wide to fit.
But the current trend is dropping in GM's LSx all-aluminum V8. Much lighter, more compact, more powerful.
In fact, quite a few who have done the swap say that the all-aluminum LS1 V8 is
lighter than the cast-iron 1.8L 4 cylinder that the Miata came with. Finished LS1 Miatas run ~2200 lbs and retain a 50/50 balance.
320-505 horsepower in a 2200 pound package? Fun!
