I was just pricing this sort of thing...
Patton Racing Engines has freshly re-built Trophy Truck strokers, slightly de-tuned to run on pump gas, 650 hp, dyno tested, with MOTEC engine management systems...roughly $25k - $35k.
Their website is under construction but they use Facebook quite often it seems...and there are some engines up for sale on there.
I'm seriously contemplating swapping out my 6.2 for one.
Good luck.
What block are they based off of? Will they fit in the engine compartment? If so, would custom parts be required to mount? (engine mounts, bellhousing, accessory drive, etc.)
The other problem with options like this is that most of us still want to be able to drive on the street (legally) and need to be able to pass state inspections to do so. I'm not sure how that would be possible if you weren't using the factory computer.
If nobody is going to really go after the 6.2 market then maybe it's time to start thinking about an LS swap. There, I finally said it.
If you started with an aluminum block, you'd save a bunch of weight over stock, which is something our trucks really need, and LS motors make tons of power.