The Mazda RX-510 was a concept car created to promote the soon-to-be-released RX-3 / Savanna. It was first exhibited at the 1971 Tokyo Motor Show and heavily based on the RX-3. The middle section is RX-3 / 808 with custom front and rear-ends styling. The front and rear were a take on impact-resistant bumpers. In my eyes, the rear styling works well where, as the front misses the mark a bit. The interior was stock except for the seats, and it was powered by a 10A rotary engine with a four-speed manual gearbox. Check out the wheels with rotor-style cutouts.
Source: Old Car Junkie
Images: Mazda; auto.ultimative.org