Shaggy. Dobie is correct, the '59 passenger car valley pan should have the breather tube connection on the back. Click the link below to see a valley pan with the breather tube opening. NOTE: the cover pictured is '55, '56, '57 (all T-'Birds except '57 'E' code) vintage. The 'tell' for the year is the oil fill tube connection to the valley pan. -No dome where the fill tube enters.
http://www.ebay.com/itm/55-56-...The valley pan pictured below is what FoMoCo went to sometime after 1957 for all y-blocks. -Perhaps even in '58, I'm not sure. Quite sure that a '59 era y-block valley pan looks like this with the dome AND the breather tube connection.
http://www.ebay.com/itm/1954-1...Both pictures that I've referenced have (or should have) straight oil fill tubes. Somewhere along the line Ford began using fill tubes with a bend in them for clearance purposes on truck applications. I'm not knowledgeable about when that began.
Addendum: Here's a pristine N.O.S. y-block valley pan at an insane price. Notice the straight oil filler tube, the dome where the tube connects to the pan, and the connection in the rear for the breather tube.
http://www.ebay.com/itm/351328...Hope this helps.
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a.k.a. Charlie Brown
near Syracuse, New York