tauro, sorry about losing your dad... He reminds me of someone I used to know.
Two schools of thought, 68 being the first year for 427 ribbed blocks and the most accepted was after 1970/72.
Also... Understanding there were no ribbed 406s, they were also cross-bolted.
http://www.network54.com/Forum/74182...xternal+ribs--
http://www.network54.com/Forum/74182...ide+of+block--
http://www.network54.com/Forum/74182...ing+special---
http://www.network54.com/Forum/74182...8/ID+Big+Block