For the 4.5" links, I would recommend the new 05/06 Float R or RP3 instead. By the time you buy the AVA sleeve (assuming it fits and you can find one) and then get it PUSH'ed, you could have bought a new version of the Float R. The newer versions have lower compression ratios for a spring rate very close to the AVA. This will be a big improvement over your old Float. They are also significantly lighter than an AVA (about 100g on the 7.87", I'm not sure on the 6.5").
If you have the long travel 5.7" links, the AVA won't fit and neither will most other newer shocks.