This might clear things up, I was just posting the full list over on the Big Block Dart thread. This doesn't confirm the spacing but I know it's different for 73+ compared to 65-72. The 73+ lowers were the same regardless of drum vs disk.
It also shows I was wrong about the earlier drum lowers, they should be the same 65-72. And we already have confirmation that the difference in the earlier ones between the drum and KH disk was the bolt size.