I just joined your Forum, because of seeing some pretty interesting articles. I currently drive a 1965 Mustang Fastback with a 1998 Explorer 5.0 that looks like a 289, with a T5 and a 3.80:1 rear end gear. It runs excellent with the upgrades that I have made to it. However I am now looking to build a 1966 Mustang Coupe for a family cruiser and for longer trips were mileage and driveability is a concern. I have tossed around the ideas of 1986 to 1991 5.0 and AOD from a crown victoria or grand marquis. Also another option that I thought of is swapping in a 2.3 turbo and T5. Either way, I do not want to change anything with the front shock towers. I like to keep things close to original that are difficult to change back. My fastback gets 20 MPG freeway, and 16 MPG around town, so I would hope that even with the 5.0 option in the coupe, that if I kept it stock and put a good rear end gear in a 1200 pound lighter car I should be able to hit around 25 on the freeway. Any input and experience is great, Thank You.
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Hello from Michigan, 1965 Mustang Fastback, 1966 Mustang Coupe. 
Enjoy the site!! 
