3-3 1/2 cans per gallon is what you will want to use, Stay away from any juice that has metabisulfite , sorbate , or benzoate in it. If it has metabisulfite in it you could use it but dont add any extra before adding yeast as it will hinder your fermentation. They come out pretty good.
SteveProbably metabisulfite not sulfide.
I doubt it will cause much trouble if you use a good quality wine yeast. But let the juice sit for 12-24 hours before pitchingthe yeast. This will allow a lot of the sulphite to dissipate.