OK, I am pretty sure you can, but some kid was trying to tell me that regular BBC heads and other parts are not compatible with the new Gen VI GM performance depot engines. Is this true or not?

Mark IV heads will not go on a GEN VI, I think the water jackets are diffrent. Most after market heads will work with Mark IV, Gen V and GEN VI. The Gen VI also uses a diffrent oil pan and timing cover, I also read that a double roller timing chain will not fit under the GEN VI timing cover. Also you can't use flat tappet cams in the gen VI. I think there is some other stuff I forgot, there are some tech articles on the Gen VI blocks on the chevyhiperformance site, also check out chevelles.com forum lots of big block guys there.