Lexus IS-F engine in a Miata? That would be fun. Finding an engine for sale is pretty easy. Ebay searching tells me they cost around $5k. I can’t find the exact weight of the IS-F engine or Miata engine. But the V8 is all aluminum and with that in the car I wouldn’t be running power steering, AC, or cruise control which would save weight. Not exactly the easiest swap but hey....