What is real oil capacity, manual/dealer discrepancy

[bark3rd]

I was in the process of having my oil changed for the first time and the oil change place said my car takes 6 quarts (including oil filter). My owner's manual says 5 quarts-I called the dealer and the guy said 5 and then shouted accross the shop at another tech who yelled back "it's 6 you dumbass!" whereby the first guy said "well, I guess it's 6 then". I had 6 quarts put in and now the dip stick reads above the full line. Oil change guy says all Ford dipsticks are inaccurate and not to worry! Who is the dipstick here?!! Should I have trusted my owner's manual? I put in synthetic 5w 30 Mobil and redline my car constantly-I dont want to have too much oil in the engine- help! I swear no one in this town knows diddly about cars, someone could make a fortune here by opening a decent performance shop.

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Black 2000 GT,5 spd,17" wheels,4:10's,flowmasters Steeda pulleys, timing adjuster, K&N filter