The internals for the RB 440 HP's were all the same. The bosses were also common but only the M Codes got drilled and tapped. Having said that, some C body big blocks had drilled bosses too. The left side exhaust manifold is peculiar due to the raised block (RB) and slightly different to the 383 B block (B) which was used in the 383 cars. Also the oil pan was different since the engines set lower in the crossmember so as to give top side clearance for the air cleaner. There is a "notch" in the front of the pan so the tie rod could clear when turning. The 383's and 440's got a beefier idler arm, more weight from the bigger motors. There were some other oddities but I won't go on. Hope this helps.