Can you get the engine built to any desired bore size? Is there an additional charge to run a 4.125" bore- essentially a 400?
If those heads can be proved to be up to snuff you may have a pretty solid package there, granted its nothing extradorinary but at that price its a pretty good deal if the materials and machining are quality.
decent crank, decent, rods, good pistons, good bearings, decent cam, good block. all at a pretty nice price.
I would change a few things if I was building it (namely heads and cam), but perhaps its not such a bad deal for some people.