My 2000 NB1 I've been building for 5ish years. The engine's mostly stock but I've spent a lot of time on maximizing its cornering ability on a reasonable budget and removing weight where while retaining creature comforts like carpet and a radio. It's my third Miata and definitely my favorite! IMO, NBs are the sweet spot between power, complexity and daily-ability.
I just finished it! It's a lightweight fiberglass top. It was quite the project but the end result is definitely worth it.