No proof on this, but the E58 coded motors were supposed to have hand picked parts off the assembly line with tighter tolerance's. Again, hear-say on the block, but for sure they came with things like HD water pump bearings, special silicone valve cover gaskets, nimonic exhaust valves, double roller timing chain / sprockets, windage tray, HD bearings, HD manifold castings, extra clearance for valve stems / ring lands, specially selected cast iron crank ( no under cuts form the factory ). Fifth didget on the vin will be an "L" to designate E58 motor. The 2 that I have had sonic tested have had walls in the .2 range. On the other side, ran a 71 block out of a motor home for a few years ( in the 500 HP range ) with no problems.
I've got a 1975 E58 Block stashed in the shop. I think I need to have it sonic checked.
