ls6 ls1 blocks are the same right?

hey this is my first post and prob a stupid questin but im gonna be buying an ls1 block off summit soon and i noticed whenever i type in ls1 blocks on the search bar everything comes up ls1/ls6 so im curious to know if there the same block and if so does that mean i can use ls6 heads on an ls1 block or do an ls6 setup on an ls1 block?

They are virtually the same. The LS6 has small windows between the bays of the crank case to allow for better oil flow between them. But they are still interchangeable if you are building a motor. In fact, a small number of '01 & '02 LS1 F-Bodys left the factory with LS6 blocks.

More info:
http://www.idavette.net/hib/ls6/page3.htm