Some great info on Mexican 302 blocks

The is a U.S. made casting that's as strong as the Mex, but lacks the big main caps. (ain't seen those break anyway) The casting is D8VE. This one weighs at least 10 lbs more than most others. 136 lbs total vs 120 for the early 80's block, and 126 for the roller blocks.
 
My local machines shop attributes it to the metal they used. It's a good bit softer, allowing flex. They've rockwell tested many of them and show they are an average of 20pnts softer than normal blocks.