There are some things you can do to make a 617 somewhat faster. Also, 603 and 606 engines have been installed with some difficulty. However, if you are looking to go fast for cheap, you have the wrong platform. I will suggest Kawasaki ZX-6R and ZX-10R as ways to go very fast for not much money.

See below:

http://www.youtube.com/watch?v=inc9cGasgsA

This guy spent way less money on his bike to run a 7:10 at the 'ring than it would take anyone (Vettel included) to run ten minutes in a W123.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.