I'm looking at getting an '04, '05, or '06 Stratus, most likely with the 2.7 V6. If the car does not have autostick already, can I add it? Is it just a matter of swapping out the shifter assembly, or are there more parts or a different computer required?

 

Not 100% sure all the parts you need, but at the least you'll need the autostick shifter assembly, as well as the TCM that is attached to the top of the transmission.

 

I just read elsewhere that pin 55 on the TCM is the autostick input pin. So could it be a simple shifter swap if the wire is already in place? Surely the programming is already there.

 

I successfully installed autostick in my 03 Strat 2.4L. With the 2.4L engine this wasn't even an option on the car but it works.
So here's what I know from doing mine and maybe you can take all this information and apply it to your car. First of all I have the NGC PCM in my Strat, which means the ECU and the TCM are combinded in a box with 4 connectors on it. I'm not sure if in the later years the 2.7 got switched over or not but 03 was the first year the 2.4L switched over, the 2.7 stayed the same with 2 seperate boxes still.
My car was already wired up for all options uncluding autostick and mine was a base model with manual everything, so the wiring harnesses should be the same for all models, at least for mine it was.
If you already have the autostick connector under your center console you're all set there. Some people needed to wire their own connector there. To do this you either have to add 2 wires to the TCM or to a connector under the dash, then you need power and ground added to the connector so in all you need 4 wires. The other 2 wires are for shift up and shift down. For the connector I just used a 4 pin cd drive audio connector from a computer.
In my car it's the cluster that determines if autostick is installed are not over the PCI bus. So I needed an autostick cluster or nothing would work. I believe the cluster also controls whether or not you have ABS installed or not, so make sure that matches up. If your car does not have ABS then you need to find a cluster from a 2001 ES model, only year and trim where ABS was an optiton with autostick.
You will also need the autostick cluster shifter assembly with the switch installed. The shift boot is optional, you can still move the shifter sideways with the original shift boot and bezel.

There's just some basic information and a rough tutorial on how it all goes together. If you have any other questions just let me know. The one thing I'm not sure about is if the 04+ models with the 2.7L use a TCM still or if it's over to the NGC combined PCM.

Good luck.