Longer shackles WILL NOT raise your car. They will however do the following: Bend the rear section of your springs downward ruining them. Wipe out any hope of a good hook-up and launch. Flex like crazy from side to side. Look stupid.
Now if you want to reduce traction, cause wheel hop, and have that silly 70's look there are better ways to do it. An OEM type spring with a slightly higher arch will do nicely. Also, if handling is important, set the rear at factory height, and lower the nose slightly to give yourself a 1-2 degree rake. ANY spring shop can re-arch your OEM springs to factory height or slightly above (remember the spring rate never changes as a spring wears, only it's camber). And the rear springs should be nearly flat anyhow, thats how they were designed.
Longer shackles are right down there with air shocks on the list of bad ideas.