The engines are bullet proof. I have done 2 swaps to date only comments I have as downfalls is if you by an NA auto car to begin with make sure to change the rear end as most come with a 4.11 which will kill an AOD if thats the automatic you use hunt for a 3.31 or 3.54. Second if you do put in an AOD make sure that it is in good condition and is a V8 unit later thunderbird SC or 92-93 302 trucks are the strongest. The Aod is the week link. The AODE is a better choice for longevity or so I am told. I have rebuilt the AOD in my current car and put a shift kit in it. Lastly, a secondary transmission cooler helps to extend the life as well which is stock on the turbo cars but not on the NA cars. I smoked the OD band in my first conversion which is quite common in the AOD unless it is in good shape and the TV cable is adjusted properly.
Good luck!