....and didja know it had a t tail to begin with? 727 fuselage stuck on a trident wing but swept forward to avoid all the droops/slats and contrivances to get the Trident airborne.
Airlines didnt like the look so conventional tail reverted to, then the fuel crisis that precipitated the demise of the 727 ended and airlines kept their old 72's.
Result? 767/757 hybrid for economies of scale in manufacture.
Trouble was, the flight deck of the 76(wide body) wouldnt fit on the narrow body 75 without a bit of jiggling around, which is why you step down to a 75 fight deck and step up to a 76, and also accounts for the unique and rather beautiful "swan's beak" look to the 75 front end. The 767 is a very conventiional Boeing look.
Now...bit more composite, winglets, uprate the engines, new avionics..wow....what a bird that would be. A narrow body 787 for a fraction of the cost.