On the '66 440 models it went here, on the '66 500 models it goes beneath the "Coronet" script behind the wheel opening. Just to be clear - mine are not exactly in the correct position. This car was wrecked many years ago (by my uncle John) so these fenders are standard V8 fenders. I located the 4bbl emblems to cover up the "V8" holes. They should be down 1/2 inch and back so the left edge of the emblem is in-line with parting line between the 2 pieces of the side trim. When and if I ever get the car painted I'll correct it.
Just me.. but the only time I've seen a 383 emblem on the front if the fender is on a car that was in a sales brochure and for the car show circuit. All the other ones I've seen had it on the rear.
I love Mopars so much I'm date coding the skid marks in my underwear.