I actually considered doing this same swap to my 69 390 4 speed AMX. I posted a thread here on Moparts,stating that I was getting fustrated trying to find a 390 engine for my car,and was considering putting the 5.7 Hemi I had just purchased in the car. A fellow Moparts member offered to sell me a complete running 68 390 engine for my car,so I bought it from him. I will be following your thread to see how things may have been had I gone that route! Cool project!