You are going to need an air compressor and an air driven angle grinder. Go to an automotive paint suppy and buy an assortment of 2" and 1" grinding discs. You will need coarse 37/50 grit and medium 100 grit. They are about $1 each. A little less if you buy a box. A die grinder and some burrs are also helpfull. With these discs and a little time you can remove just all of the casting flash, unnecessary numbers, and the cast iron grainy surface. Don't take off any more than necessary. Keep the discs moving and apply light pressure. When the disc stops cutting replace it. Put several layers of duct tape on the machined surfaces. At the same time go inside the block with the burrs and remove any flashing. Once you have sanded the block to a shiney and smooth serface apply a high fill primer and wet sand smooth. Your block will look like glass. Plan on spending a little time. Bondo is a short cut.