For what its worth, there arent that many MONSTER miata's. They only built 90 or so of them. Monster Miatas are Monster miatas, built by Monster Motorsports/LaForza in Escondido. The cars of lore, featured in magazines and known world wide...V8 miatas are V8 miatas, often piecemilled together in someones backyard, with little skill and no thought to drivetrains, rear ends, suspension, chassis etc.
Monsters were completely reworked and done right, from chassis to rear end.
There are a few "shadetree" home swaps out there built by people who are flying by the seat of their pants and questionable at best in every way shape and form. Scary!
I have a Monster Motorsports miata for sale in the Classifieds here. Its 100% reliable and VERY fast...and it handles well.
Yes, I suppose I have a vested interest, but I'd tell you if they were hunks of junk. "True" Monster Miatas are nice. I also have turbo miatas and they're totally different beasts..both much fun in their own right.