All the big block engines will be with in a few pounds of each other in weight, all have the same external dimensions, and mounting holes for the engine and trans. There are way more 454 cores around, so you get a bigger engine cheaper as for a core and it will not cost any more to build, and some parts are actually cheaper because of the volume. Now, there are some raised deck truck and marine engines, but I am assuming you would find and build the more common standard deck block.