The 7 after the casting number I believe is the casting mold or mould number for this block. I have seen 6 7 8 10, was there 1 2 3 4 5 and 9. Was there any numbers after 10. Makes you wonder if Chrysler did this on any other blocks such as Hemis, 383s between the 1968 to 1969 build. Hemi might of been a little more tighter on when they were build and assembled, but this is Chrysler after all and anything goes. Love to see an early HP 440 motor from 1969 with no machined pad and a serial number on it and people start saying the block was restamped. Good stuff Mccannix.