The later blocks have lower nickle content as well.
If I were going to build a 600 HP motor with 8-10k invested in rods and pistons, I'd opt for an early standard bore 400 of any code, including a Catalina or Lemons. 67-69 GTO or Firebird block and crank $800. Same year Cat, Lemans or GP? $300-400. Same block, just not a desirable correct "code".
It's piece of mind, insurance and assurance of my investment of machining and parts.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
