I have a 40 gallon fat boy with an a/c unit above it. I can get the old anode rod out as it has deteriorated enough to bend but how will I get new one in without removing a/c unit or draining and moving hot water heater. Is it possible or do you have another solution?

Depending on the situation and clearances you may be able to bend the new anode in the middle then straighten it against the opening as you insert it. If you cannot straighten it enough you may end up hitting the dip tube of the cold supply or the inside wall of the hot water tank while attempting to threading it in. That would make things difficult. I've heard tales of plumbers cutting the anodes shorter, but this of course would shorten it's life expectancy. Also consider that if the anode is already so corroded that you may want to thoroughly inspect the hot water tank for problems.