5.3 input
That being said, your engine is a really good starting point as it should already come with the better flowing 243/799 heads and flat top pistons (for better 9.9:1 compression). Depending on what year the engine is it might also have the better flowing truck intake which may be ugly but works really well for a stocker. Here's some additional info about your engine in case you want to know a little more about where your baseline is at: https://ls1tech.com/forums/generatio...-lh6-info.html
Good luck with your project dude sounds like it's going to be fun when you're done

