I am thinking of converting my 70 340 4spd. Duster to an automatic in the next year or so. Is this a big job? Do they make a shifter that will go in the factory tunnel cut out? (I don't want to cut the floor). What would I have to change. I would like to start gathering the parts. All advice is appreciated. Thanks.

Not a hard job, definitely easier than going from auto to manual. Should be able to raise some decent $ selling off your used parts. I would not convert from manual to auto myself unless I physically couldn't drive it anymore but everyone has their reasons. Basically all you have to do is bolt in the trans/torq converter with a new flex plate and go. Make sure you get a converter that's got the necessary balance for your engine. An aftermarket shifter can be placed where ever on your floor and not look too bad. Then run a kickdown linkage from the trans to the carb, you can scrounge up a stock piece or buy an aftermarket kickdown cable. After that it's basically dealing with driveshaft lengths to get something that works. May need shorter or longer depending on trans type you go to. Then run some transmission cooler lines to the stock cooler if your rad has one or to an external trans cooler.

Thanks for the reply. What about the Trans mount and member, is it the same for an auto?