im pretty sure the internals are stronger in the 3sgte , but not 100% on this ( crank, rods , pistons, bearings etc )
I cant see why you couldnt NA a 3sgte block - and retain the same head/intake side of things , and just use a good set of extractors to backstep by removing the forced induction gear ..
Then again - Why would you bother ?
Are you looking for a high revving cammy 3sge setup ?