This BMW Z4 coupe’s model year isn’t mentioned, but these relatively rare factory hardtops were made from 2006 to 2008. Built by a German tuner, the car has given up its original straight-six for an 8.3 liter Dodge Viper V10 delivering 550 HP to the rear wheels through a 6-speed manual. The seller says it was built with reliability and safety as being key, adding that performance is “brutal.” Fully registered and street ready, it looks very mean and quite well put together, too, Find it here on eBay in Saarbrücken, Germany for 49,500 euros (~$55,600 USD today). Special thanks to BaT reader Chuck G. for this submission.

The car looks virtually all stock from the outside, albeit with black painted OEM BMW wheels and giant Audi R8 sourced brake calipers peeking out from behind. Stripping them back to bare metal and refinishing with a factory like clear would introduce some needed contrast, but the car itself looks to be in nice shape.

The cage looks really well done, and is tied in at key suspension mounting points. The bright neon yellow/green color it’s been finished might not please everyone, but it certainly stands out, and the above image nicely shows off how much work must have gone into its design and construction.

The interior isn’t shown directly, but appears to house at least a partial custom dash, while door trim panels, seats, center console, and everything else is clearly custom. Note what appear to be very large, very plain looking levers for the shifter and handbrake, the former of which operates a Tremec T-56 6-speed.

The Viper motor itself sounds to remain untouched, with output given as 550 HP. Total weight is given as ~1400kg, and 51%/49% front-to-rear weight distribution reportedly shifts to very nearly 50/50 with a passenger in place. An automatic exhaust valve opens at 3800 RPM (and can be kept open, too), underneath which the seller reports that the car is actually quiet. Suspension is said to be well tuned, though the seller sums up the driving experience as “brutal” regardless.