Tom Brady will be saying hello to an old nemesis Sunday when his Patriots take on the Cowboys.

As for just how old a nemesis Dallas might actually be to the New England quarterback — well, the enmity apparently goes back 42 years and 109 days.

Or, as Brady put it Wednesday at a news conference, “I’ve really not liked the Cowboys since coming out of the womb.”

The Northern California native explained that eye-opening line by referring to the fact that he grew up a 49ers fan. A few years ago, he shared a photo of himself as a young boy in 49ers attire who had the good fortune — although you wouldn’t know it from the expression on his face — of attending the 1982 NFC championship game at Candlestick Park. That contest became legendary for “The Catch,” a leaping, late-game grab in the end zone by San Francisco wide receiver Dwight Clark that helped defeat Dallas and send his team to its first Super Bowl….