Three pictures exist of the puzzle car. Front, rear, and interior. After further research, the car appeared at a show in Burges in 2000.
Multiple forum posts speculate that the Viper MX5 body kit was produced in Germany by Buethe Motorsports. That company went out of business in 2002 or 2003. Their assets were purchased by another German company called Tenzo-R (no connection to the Japanese firm). Tenzo-R in Germany also seems to have gone out of business.
RE Amemiya did make a Viper front bumper for the MX5, not a complete body kit.
Rear view of puzzle car: