Pond's cast iron blocks will go 4.400". His aluminum blocks won't go quite that far. Not sure on the Shelby blocks....never used one.
It terms of accuracy, the BBM block actually *looks* more original externally. It has the plugs for the bypass in the rear of the block (they are not functional) and also the little pipe plug on the bottom rail of the block, per the original side oiler. Pond's block has a -6 o-ring AN fitting for the rear, which is the main "side oiler" feed.
The BBM blocks already have blended in main bearing
oil feeds to better match the bearing holes and a few other tweaks, such as tapped deck
oil feed holes, to help the builder out.