I have an A-518 transmission in my Cuda currently. It has served me well for the last 3 years. The transmission bolted to the back of my 360 with no problems. I did'nt try to connect my trans-fluid lines to the radiator. Instead, I ran them to a separate trans-fluid-cooler. The fun comes in supporting the back of the transmission. The floor pans did not have to be cut or modified. I had to remove a U-shaped piece of metal that runs above where the cross member would bolt. This allowed the clearance I needed. In addition to this, I has to modify the cross member to allow the back of the transmission to mount about 2 inckes below where the 727 would sit. Of course the drive shaft has to be shortened a bit and the whole thing works very well. I've experienced no vibration or alignment issues. The original floor mounted shifter hooked up with a little modification to the shifter bracket that bolts to the bottom of the 727 trans. The conversion does require a little fabrication, but most of it is straight forward and self-explanatory.
On a performance note, the A-518 completely woke up with the addition of a Transgo skift kit. The car felt very responsive and crisp with the shift kit like a performance car should.
In conclusion, I would say that the benefits of having the overdrive along with the 3.91 gears by far outweigh the troubles with the installation. Interior noise levels are lower, better gas mileage and sustaining highway cruising speeds make the car much more practical.
