I believe those extra holes are on the passenger's side only, for the offset motor mount used with the 292 inline six. Changing motor mount positions will affect a lot of other things, such as driveshaft geometry, clutch linkage, fen to radiator clearance, etc.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!