Possible auto transmmision infusion

I posted recently about my M5R2 tranny going to gear heaven and I have some bad news. They are hard to come by and when you do find them they are HIGH.
My question is... Can I put an Automatic in it with out a lot of problem? I would like one with overdrive but I am not familiar with Ford Transmissions. I Know of C4's and C6's but that is very limited.
All I use the truck for is hauling an ATV and short runs to supply stores no further than 120 miles round trip. Would an automatic with out overdrive kill my gas mileage ( I expect some loss), I think the truck has 2.73 rear gears, and a damned strong engine.

So what I need to know is:
What transmissions will work with a 1993 ford F150, 4.9L, short wheel base 2WD
and how much fabing am I looking at?

You'll need an AOD trans. AND flywheel, crossmember, driveshaft, and maybe a differant starter.

Then there's all the shift linkage (for passing gear and lever position) and a lot of fabrication to connect everything.

I know that it will be a pain to change over to an AT. So I am Going to try to find a replacement 5spd. I have a doner truck that has a bad AT in it. I even got a free AT from a friend, he says it is an AOD but I am not so sure. I am going to check the ID. But like you said , it will b easier to go back with whats is in it. Thanks