My 71 cuda with the 472 hemi, 2 Carter 750's, 3.23 gears, gets around 7-8 MPG if I'm in cruise mode, probably around 5 if I'm having a little fun with it.
The 74 with the 360, auto with a TQ and 3.55 gears gets around 12MPG in local driving.
My 2000 CTD 2500 4X4 gets around 14 in local driving, 22 on the highway, and around 15-16 towing my enclosed 22 foot trailer.