I used a 76 block. Don’t remember the numbers, but it was by far better than the 71/72 blocks I had at the time. Over the years, the bores did get a bit barrel shaped. Never any issues with the “thinner” main saddles. If I were to build another, Id sleeve it and run a smaller piston. The weak part of the blocks in my opinion is the cylinder walls. I used that block from 1992 until I sold the car in 2006. First year it was together made 776 hp on the dyno. When I sold it it was making over 1100hp.