I don't remember the year---but last part of the 70s--as bigger motors were beginning to be the light at the end of the tunnel--I met 3 of the top GM back room guys at some place (might of been at Ann Arbor or Detroit Drags) I still have the phone number in my old little wallet phone registar(and written on the wall by the garage phone)I ended up with 3 of the first 7 bow tie big blocks----I was building them to the requested 496 size aaaand low and behold wouldn't you you it but I was tired from a long flight and the boring bar slipped on the one that was for me!!!!!it was necessary to go out to 4.560 on the bore size(wasn't any rings available bigger) made it at 522 inches with stock 454 steel crank---one of the first prostockers to run 7 second pass---I still have that block but have sold off all the top parts and bought more modern heads,etc three times to rebuild it but have ended up selling the heads, top end and rotating assy to customers who put them in Dart blocks--back then it was good to know someone at GM and also at perfit circle who would order the wire to make the rings for wierd combos---