The bolt holes and the dowel holes go all the way through the flange, and if one is missing there will be a massive oil leak into the bellhousing/clutch area. The PO of my 59 model 3800 left one flywheel bolt out when he rebuilt the engine, and it ruined the clutch in less than 200 miles after I bought the truck.
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!