Here is something you might consider. I have no personal experience with this particular opener but I recommend the manufacturer highly. You should be able to call any Liftmaster dealer in the yellow pages for more help.

http://www.liftmaster.com/cw/product_model/0,1064,uid-iWuAbmFkamplZQ==_1497-id-233,00.html

I am assuming you don't have low headroom track installed. I did not check the link Don has provided you with but, if I had to guess he is recommending the residential jack shaft which is an excellent opener but is expensive. Another thing that would work is installing quick turn brackets on the top section. The brackets themselves are about 40 bucks and you would have to buy two more rollers which cost a couple bucks. They would take the place of your top fixtures that are currently on the door and are fairly easy to install. They would give you enough room to install the opener as well. Good luck.