Another thing; One of the things in favor of a new aluminum block is modern aluminum castable alloys suitable for engine use (355-T6 comes to mind); they are FAR more stable than what was used in the past (i.e. on the orignial GM ZL1's.) With the modern alloys things don't move around nearly as much as the old stuff, it's much more resilient in terms of thread strength, etc. Most of the time you don't even need a helical thread insert with the modern alloy as you would with the old stuff. Some of the old aluminum alloys used would tear the threads out just by looking at them funny.
