Delta customs are usually a bit more than what you can get off the shelf from Kelford or Gsc, something around $1,000-1,200 for a set. Kelford will do custom grinds too though, I don't think they charge extra for it either.
I don't have experience but I'm sticking with GSC Stage I's for mine. Stock turbo will be used after I get done building the engine, but I figure I'll go the rotated GT30 sized setup or Dom 1.5/2.5 sized turbo... Somewhere around 50 lb/min.
In your case, GT35 size with a 9k redline I would want it to breathe more up top and would get a little more lift, while keeping it around 272 duration. I don't know that your heads are holding you back as much as the turbo right now. Just about every other 20g falls off at that 6,000-6,500 area, even on 2.5's. The best would be upping the turbo now and seeing where the power is made at, then changing out the cams.