Yes ... the block was different. The oil filter was raised for clearance. In fact, the V8 Nova blocks had a spin on filter ... before the rest of the V8 small blocks did.
I have been told ... that the LT1 new style blocks have a different motor mount position than the old standard 58 up conventional SBC we all have grown used to.
I do not have PROOF of that ... but have heard it from different sources.