The SRP 213453 pistons are $560 at Summit while the ICON 823 pistons are $627 and the Ross 99495 pistons are $690. I think these are apples to apples prices but you have to double check to be sure. Diamond also has a shelf piston but they sell direct so you have to call them for pricing.

I'm sure that Molnar also has a 6.535 rod and his prices are usually really good. The SCAT rods are $485 at Summit with the standard bolts which should be fine for your application. You can put together a total stroker kit for about $1900 from Summit. If your engine builder has a wholesale account with Summit then they get an additional discount.