I'm not going to comment on the ford-in-a-mopar side of this swap, but I will say that you'd probably make just as much power with a worn out slant as you would with a 289. They are turds, and the slant is way more reliable.
-Tim
289's can get a good penny.....I would say that you could sell that for enough to get two 318's. Heck I would almost give you one if you wouldn't do it.
Motor mounts and tranny mount everything else shouldn't be that big of a deal. You could even use the mopar ignition system with a little splicing here and there. Go with a slant radiator and the upper hose will be no problem, lower hose won't even be an issue. Distributer placement will be the main give away if it is dressed up like a mopar.
For all the effort to install a 289 v8 and trans, driveshaft mods, exhaust, etc. I would rebuild the slant or get a good running engine and swap it.
I did the reverse in high school. 67 ford f150 short bed with a blown motor. I made some motor mounts, dropped in a 225 /6 and trans. floor auto shift, Stock Mopar drive shaft bolted up to the diff and I used the ford wiring. It ran great!
I got blasted a few years back when I talked about my Ford 5 speed swap in my 65 Barracuda. My A-833 locked up in 4th so I mounted a spare T5 behind the 318. My 7 1/4 broke so I installed a 65 Bronco 9" I had laying around. And, I'm a 65/66 mustang guy, so I mounted a stock 65 mustang driveshaft in between the trans and rear end, perfect fit. I have Ford engine laying around but I still rebuilt the Mopar engine. No one can see the Ford parts without close inspection. I wouldn't feel right having a 289 under the hood. My experience, it will be cheaper and easier to install a Mopar engine.
In my 66 Mustang, I have a Viper T56, made my own adapters.