My fastback came with a C4 green dot which I just recently changed to a 82 thunderbird C5. I am using my car more especially on the freeway. My mechanic has an 87 mustang AOD which he says will give me an extra gear to cruise better. I would like to know of the guys who have done such a swap feel it was worth it. I just spent $500 on the C5 upgrade; this AOD will cost about another $500 to $600. What do you think?