McLaren 650S 3.8l and gearbox and put in this:
1991 Volvo 240 where the middle row of seats is now. Put Öhlins coilovers and JP Racing brakes all the way ‘round with a custom built IRS in the back. Put a fuelcell in the front. Tint the back windows and put what fits of middle row seat back in over the new engine cover/firewall. Get a push pull shifter lever to work with the transmission that looks like the stock shifter. Stiffen the chassis with a lot of bracing. Build a roof scoop to feed the engine, but hide it in a Thule roof box. Put the stickiest tires possible on the stock wheels. Leave the rest of the exterior as is.