Hey Carl,
I know we've been p/m ing back and forth regarding classic Mustang shopping. I'll throw in my two cents.
I'd say first you have to look at what it is and how much they are asking,Sounds vague but here is how I look at it.Pretend it's one of the cars you listed and they say the price is $5k,assuming it's not a scam(we know about those,right?) I'd look under the car to make sure it had floor pans, I'd get the paper work, and I'd quickly drive the car home so I could tell everybody what a good deal I got. That's my advice for Cars priced below the market........
So basic questions to ask for a new shopper,assuming the car is priced at or above the market . In my order.
The most important is rot,I'm not talking bondoed quarters, or bad paint. I'm talking Rotted rear frame rails around the spring shackles, Rotted front frame rails in behind the shock towers,near the steering box,in front of the shock towers especially under the battery tray this is a very common rot area. Rotted cowl vents under the dash(ridiculously common),Rotted floor pans all models, On convertibles the inner rockers and torque box assemblies(also very common) I've fixed a bunch of these. 67-up all models have torque boxes they are prone to rot. So this gives a general idea. I can speak from experience when I say that rot is very common and very often it is repaired improperly and covered by dealers as well as individuals. You would be speechless if I told you some of the stuff I've seen, some highlights I've seen cowls stuffed with newspaper then bondoed over,wood yes as in 2 x 4" 's placed inside frame rails then bonded over and painted black to creat the illusion of being a frame. Aluminum flashing used to wrap over bad rot out (yes like you wrap a rotted window sill) and then bodyworked and painted to cover up. So this is my biggie.One rule with rot especially underneath when you see some you have to figure you're only seeing about 50 percent of the damage (if you're lucky) you don't realize the full gravity until you start cutting usually.Mustangs are uni-bodies so there is alot of metal overlapping(or as I call it sandwiching)So when one piece goes bad it usually takes one or two of it's neighbors with it. Rot/rust is the most time consuming and expensive phase of a resto. Which is why most body shops stay away from doing it.
So that's my biggie, the first thing I do when I go to look at a car is get under it and crawl front to back.
Next I guess other types of rot. Doors,wheel houses, fenders,quarters, this stuff is serious as well. These I would look at from the perspective of I figure out the price of the replacement part,labor and materials. Ok so enough about rot.
So the first question would be rot.
next questions in no particular order.
condition of drivetrain(engine ,trans,rear)
condtion of suspension
condtion of brakes
" " of Paint
" " of chrome and trim in general
" " interior (this believe it or not is one of the easier and cheaper areas to fix)
What options does it have
You can look at the door data tag and decode it,on 67-later cars you can buy a marti report.I'm a fan of paying up for options and such.
What work was done to it and when (basic car buying stuff)
do they have any progress photos? These are a bonus,they help get an idea if the work was done well.
You want to look at the car during daylight and take your time crawl all over it.If you can bring someone with you(a car person is a bonus) If not bring anyone they may see things that you don't.
another thing I like to do now since digital cameras came out(it's one of my favorite tools) is to take pictures lots of them I can't tell you how many times I'm reviewing the car thinking about buying it looking at the pictures while drinking coffee and I see something I hadn't.
I try to stay away from "Dealers" No disrespect but unless they are classic car specific they're usually the worst .Don't get me wrong there are plenty of shady classic car dealers as well. Sadly Ebay and such combined with Barrett Jackson hype has spawned an industry of people slapping together cars and blowing them out over the internet. So this is a big buyer beware,once again do your leg work. I can't tell you(but I would if you've like to hear some stories) how many times I've had dissagreements with classic car dealers(usually I'm there because I'm helping someone evaluate a car before they buy it),because the dealer was trying to B.S. me.
A last very important part which we could discuss in detail,people write books on it.Is rare /performance cars i.e. The Bosses,Shelbies, Hipo's etc. Very often with these cars their value is a sum of the parts. You've got to look for and ask about specific parts .This is very important because replacing this stuff correctly gets to be hard and expensive.This is a case by case kind of deal.
Important bit for "Rookies" Try to get a knowledgeable impartial person to look at a car and tell you what they think even if you have to pay them,it's worth it. It also helps to ask people on Forums like this,I know it's over a distance but post photos you'd be surprised at what people who know what they are looking at might see and point out to you.
So I deviated from the ask questions theme of this mainly because as they say knowledge is power.The more you have the better the deal you will get. Seriously My best advice trust no ,one sounds harsh. But it's true sometimes people will tell you want to hear(because they are lying to make a buck) or they simply don't know. So it always pays to view the car in person and question whatever you see that doesn't appear right.
I think I have written enough for now,I'll probably add more later.If I've seemed vague it's because it's best to have a general idea of the market and you really have to look at these cars on a case by case basis because each one is different and it will have it's own unique problems as well as price. If anyone has any specific areas they'd like to discuss or they have questions in general regarding classic car shopping please fire away,I'd be more than happy to assist in any way I can especially if they have a particular car in mind.