[markjohnson]

Well, if you check the older Chilton's manuals from the early-70's, you'll see there is actually a code for a 1970 454-450, aluminum head engine, listed as "CRS". I've even actually been around one of these "CRS" blocks and can vouch that they do exist. A friend had one in his '69 Camaro in high school and had installed a 396 crank into it, making it into a 427. Now I was around about 4 different LS-6 cars back then and I always told him that his particular block was pretty rare and he needed to be careful with it and one day the air cleaner stud fell back into the secondaries about one block from home and window'ed the block. Now if "CRS" comes up as something else instead of 1970 454-450 hp, Alum. head and is maybe a mistake in the Chiltons' manual, I'd love to know. But I do know that there was at least one 1970-dated "CRS" block.