Well, I dropped my truck ('88 Chevy) 5"/7" using mostly Bell Tech stuff. The spindles say, not to be used with wheels that have more than 3.5" of back spacing. Mine are 5.5" of back spacing.
I now know why they recommend this. The inside of my rim has been ground down by the lower a-arm. I am no expert on lowering by any means, and your vehicle is different than mine, but I would not recommend just spindles if you have custom wheels with more than 3.5" of back spacing. I would probably recommend lower control arms. I would ask the sales people though about the angle issue and if the lower a-arm takes that into consideration.
Course my real recomendation would be to bag all four corners.
Good Luck
One more thing..............stay away from the Drop Shop out of So. Cal. They are crooks.