If I were a low-budget film director, I would take a car with an switchable blower only for one of this reasons:
1) Because it's already done, and someone sells it at a fairly low price
2) Because I'm mad about cars, and want to throw the whole money in such thing, letting the MFP police wear vinyl jackets
3) Because it's simply not true, and it was faaar more easy to put a fake over the engine, and get the film done.
You know, if there are different possibilities, chances are that the correct is the one that sounds simplier...

Well.....Number 1 can't be, because of the fact that such an engine would be anything but cheap, and that the cars seems to be a special work demanded to someone specially for the film...
Number 2 can't be, because, in case you had that amount of money, you wouldn't do with such a jewel what you see in the photos of this web. They surely have blown away a lot of money with the fast&furious 2nd part, but that's all plastic and alloy wheels...done in Hollywood ( not in Australia, in the mid 70's, and by an unknown director/actors )
So I guess you know the answer,right?
I would also love to believe that such a beast was real. I'm convinced that it COULD have been. But sadly I'm also absolutely convinced that it wasn't......
BTW: 200 bhp without blower is really enough for every-day cruising. My BMW M3 has 220 bhp and goes up to 152 mph top speed, doing 0-60mph in 7 seconds.... that's a muscle car here in europe already!