My advice would be to learn how to tell the difference between a 904 and 727, and the different Mopar rears, then go look at it yourself armed with that info. I wouldn't trust what the seller says it is, they may not know, or may tell you incorrect info. You just never know.
It may be close to being worth that to you if it has a good transmission, and has had an 8.75 rear swapped into it, but that's probably unlikely.
Rebuilt 318's are usually pretty cheap. Especially if they have no documentation, because then you are taking their word on what is in it (if they have any idea), and you don't know how well it was put together or planned. Could be a ticking time bomb if whoever put it together didn't know what they were doing.
So, for it to be worth even close to $1500 for your intended use seems a bit of a stretch, but it depends on what other parts you can use are on it. That's just my opinion. Go look at this just to rule it out or maybe get it real cheap if the real info and situation is better than what we can tell with that simple ad, but otherwise, I would personally look for a good deal on a rebuilt small block preferably with documentation by a reputable builder, then find the rear end and trans you want separately.
EDIT: Good point above about the other V8 parts (torsion bars, K). If there isn't a V8 K in there, then maybe they used the Schumacher /6 to 318 mounts, which is fine too. Keep in mind everything you will need for your conversion. In addition to all of the above, new driveshaft, radiator, possible brake upgrades. (Looks like the car in the ad has NOT been upgraded to front disks). It's not a cheap conversion usually. So, the more you can get cheaply in one deal, the better. If this car has a lot of that already, and you can get it cheap, then maybe it wouldn't be so bad.
