I bet the chevy V8 is wayyyy faster than the 6 cylinder the 914-6 came with. If you were building a full on racecar like that why would you use a slower, less powerful, and much more expensive engine?
That must be the Mercedes SLR Stirling Moss. According to some information I have here 75 where built for a price of at least 892.000 Euro. Supercharged V8, 650HP, 350 km/h and 0-100 km/h in less that 3,5 seconds. I guess you need a helmet if you drive this bullet WOT