Engine numbers

Ok, I went through a bunch of blocks around that year and this is what I found.....
All my '64-6 273 blocks (about 10 of them) have the 2465330 casting number.
(2) '67 273 blocks with the C273 stamp in front are cast 2806030-273
(2) 68-9 273 blocks stamped PM273 are the same casting number.....2806030
(1) '67 318 stamped C318 is casting 2536030
(1) '69 318 stamped PM318 is also cast 2536030 as well as a dozen other 318's I have so I can only conclude that the book I have is wrong unless someone else here can post a photo of a 318 with the 2806030 casting number.