Do lt1 aluminum vortec heads have more valve seal clearance than stock heads?

 

I'm not sure about the aluminum versions, and not sure about which other stock heads you might be comparing, but my iron LT1 heads had factory positive seals and room for LT4 retainers/springs with 0.525" lift without interference.

 

Of course, that wasn't quite enough for what I wanted, and the guides got machined down at the same time the seats were enlarged for bigger valves lifting to 0.540.