Dubious about the 8.25 rear. The 7.25 was pretty much standard fare in /6 A body units. Though someone could have swapped in a 8.25 out of a M body when the 7.25 went boom.
What else...
Nice cars, nice lines, basic car
Came in many flavors. Back then options were your choice. I have seen 13" tires, foot operated washer pumps, single speed wipers. Auto was a 904 and I don't remember what the manual was. Carb was likely a Carter BBD or a Holley 2bbl. Ignition was point and coil, though you can easily convert to Electronic ignition by swaping a distributor and box in.
Brakes, came in small and smaller. Should have 4 wheel drum/shoe setup. The larger brakes came on the 14" Wheel models.
You will find few creature comforts in that car. It was one of the base models in the Plymouth line.
Other than that, it's all standard Mopar stuff. Body parts, including floor pans are available, but not from DCX. Most of the /6 performance parts are out of production (maniolds and such).
The V8 and /6 K frames are different, so you can't just bolt in a V8 with out some thought.
More info:
http://en.wikipedia.org/wiki/Plymouth_Barracuda
What does he want for it, if I may be so bold? Something reasonable I hope !