the suspension from the honda will not work, you will need a focus specific one from 00-05. How many miles are on the SVT?
A worn suspension; bushings, and shocks/dampers that are blown will contribute to bad tire wear. Also, being out of alignment will do it too (which worn bushings can contribute to that too.) If your toe is out of spec (more so than camber, but camber can be an issue too) that will eat tires. Ideally try to get your rear aligned to around -1.5 to -2 on camber and toe as close to zero as possible.
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and the part is "Focus Svt Damper Kit M-18000-ZX3, they should have the best price. Your springs should be fine unless they are rusted out/broken. Might also consider getting a set of camber bolts to help dial in your rear camber better (they are around $10/bolt)