The calipers are identical, V6 or GT, it's the caliper brackets that are different to space the calipers out for the larger rotors.
It's a cheap conversion but for what you are doing it won't net you much.
Now, if you need to replace the rotors anyway, then it is only another $75 for the pair of GT calipers with the brackets on them from Roush's ebay store. The rotors are only $50 for the pair.
As to slotted and dimpled, all that really does is add some looks but takes away surface area and they cost a lot more than good replacement rotors.