I just replaced my 99 miata engine with a used 99 from Lone Kiwi Parts Finder(.com). This was the only contact I made out of at least 20 that had an employee with knowledge of the peculiarities of these(99-2000) engines. I highly recommend these guys if you need a fair priced used motor. I paid $1200 for mine complete with an accurate endplay measurement. Motor was installed with an rb header and exhaust. Performance is not even comparable to stock.Thanks to the fellows with the advice. BTW, only 53,000 on used engine.