I have a gsr sleeve block and was thinking about stepping the block or o-ring. Which should I do or both would be better. Looking for 500hp+ goal. I was leaning more on just stepping
The block.

 

I think you will get a lot of different opinions on this topic. I have used flat decks with no o-ring to well over 900whp without issue. Finish of the sealing surfaces, prep work and installation has been the key to avoiding problems there. The devil is in the details.

 

Stepping tends to have sealing issues on the outside and O-rings can cause issues if not installed properly. For your moderate goals you don't need either. As was stated before, shoot for a perfect properly prepped block and head and you will be fine.