I have a 1970 240Z and the keys for mine only have notches on one side. (Can't turn the key upside down and put it in, on ignition and doors.) So not sure about them being for earlier models.
The book Timberwolf was talking about is How to rebuild your Nissan & Datsun OHC Engine by Tom Monroe. You can get it from Amazon.com. Another good one to go with it is How to modify your Nissan & Datsun OHC Engine by Frank Honsowetz.
Does mikuni still make a carb setup for the Z? Also would 3.1L running between 10 /10.5 to 1 compression with SU and SM needles be a good setup? (Carb flow and run on 93 octane gas?) Thanx