Quick check; look at the speedometer. If it has a sweep style speedo with idiot lights, it's not a true SS. If the dash has round guages, then it's a good possibility it is an SS. Park it on level ground. Does it sit evenly or sag to one side? Even if it sags, it doesn't necessarily mean the frame is tweaked, the coil springs could be fatigued. Remember, this car is almost thirty years old. Take a friend along and have him follow you when you take it for a test drive. Have him pay close attention to the front and rear wheel tracking. The rear wheels should be following the same path as the front wheels while the car is traveling on a straight, level road. If the rear wheels dogtrack, that is, they seem to be following a path off to one side of the front wheel track, then there could be frame damage. In extreme cases a car may actually appear to be going down the road sideways when viewed from the rear. Of course, one of the tires could be low, or it may have two or three different size tires mounted on the vehicle. This will also cause a dogtrack.
The 73 motor is OK, but it won't be a numbers matching engine. Understand that going in. If all the brackets and accessories are accounted for, then you should be alright. The Impala engine won't be as strong as the original engine. Is is a low compression engine built with smog control in mind. The heads probably have the smallest valves produced for a 350. They won't flow a lot unless you have them reworked with larger valves. With that info, don't expect it to be a tire scorcher. But hey, the fun starts when you start building that special engine.
Other than that, check the body over for signs of bondo repairs. You can usually see bondo repairs if you look at the sheetmetal panels from different angles. Look for little swirl shaped scratches under the paint. Look for waviness in the sheetmetal. It's unreasonable to expect to find a thirty year old car that's never had body work. What you're looking for is the quality of the work. Also, if the owner tells you the car has never had body work and you find obvious signs of bondo, then I'd be a little leery of anything else he has to say. Look in the trunk, and look at at the backside of every sheetmetal panel you can get to. Crawl in it, under it and around it. Try to poke through the floor and trunk pans with a screwdriver. Gently of course, you don't want to *****off the owner. It's still his car.
Last, even if you do find some flaws, don't be put off. If you think the car's condition was overstated, make him a reasonable, fair offer. DON'T, I said DON'T stand there and nitpick his car. What I mean is, don't stand there and give him a laundry list of everything you think is wrong with the car. Just keep everything to yourself and make an offer based on what you found on the inspection. Most people, myself included, hate it when someone starts in on everything that's wrong with a car and how much money it will take to fix it. I can't emphasize enough, just keep your comments to yourself and limit your conversation to the negotiation of the price, or as I like to say, the business transaction. Some people consider it an insult when you start nitpicking the car's faults. And most of the time, they'll ask you to leave their property.
Good luck and happy hunting.
