A local 4x4/ performance shop has one of those engines in the showroom, its complete with intake, carbs, and air cleaners. They have a 426 hemi complete but its got a hole in the block from kicking a rod out.
The doors are very heavy on those cars, they wear out hinges which causes them to not latch..
The 403 olds was notorious for overheating. That engine was one of the biggest boat anchors to come out of detroit.