You'll have problems with the Western voice files using the SG firmware. It's best not to do that conversion as the problems far outweigh the 'eye-candy' benefit of JCV. You'd be better off (and safer) to convert it to nuvi 465T ("Truckie's Nuvi") which will give you lane assist in the top LH corner while navigating:
All the 2x5W files are fully compatible with 465T.
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