I have a 73 914 six conversion with a 3.2 in it done right with everything modified. I can easily get $15k for the car. It has been nagging me that I have so much knowledge of 914-6 but my car is just a clone.
So I just bought a real 914-6 #200 out of Texas for $9000. Its a core car, needs everything, but a excellent 100% original start that has been sitting for 30years in a garage.
I though about stock resto, but come on guys the 914-6 is a incredible car that was factory underpowered. Porshce killed the market on 914-6 cars by putting the weakest POS 6cyl engine ever made in it. Only 110 hp, terrible. So the power must be upped, the 14" fuchs are not only ugle but you can't get good tires for them. The suspension and brakes are on part with a base 911 of similar years but can definatly use improvement.
I am a long time 914 buff, I have built 3 914-6 conversions and my current conversion is awsome with 250hp and 996 brakes. My belief on the value of a real 914-6 is that the stock will always be admired and valuable, the wild 914-6 custom car will be worth a bit more for a while and then decline, I would consider that a real 914-6 that is done up like say a 914-6S or 914-6RS as if Porsche would have built it but never did.... these cars may actually be worth much much more than bone stock 914-6 cars. I think modified but period correct will bring the much dollars on the future.
I will tell you my reasoning, true the American Muscle cars are shooting way up in value. I just sold a 68 Camaro Z28 numbersmatching perfect car for $86,000 at the last Barrett Jackson (I was hoping for $65k). But a 6cyl Camaro in perfect condition is worth $7 or possibly nothing. A nicely equipped V8 4spd Camaro that is correct can be had for $20k. A big block numbers matching 4spd car can be worth $60-80k but then add $20k if it is a convertible. If you notive the super delux rare cars are woth more than stockers because they are much more fun! Just because you have a nice Camaro even with numbers matching then it doesn't mean it can compete with a Z28 Camaro.
The 914-6 is not a super exciting car in stock form and there are no special editions or different engines, however there are factory supplied kits to build GT cars and modify the good base car the Porsche would never let beat their primary marque the 911. So Porsche supplied the means for individuals to build wild cars and never really hurt the mainstream sales of the 911. Therefore I think you can modify these cars with steel flares and big engines (although to make the most value you would need a high power 1970 motor (probably with MFI) install wild Fuchs alloys (but 15" wheels only), an d basically build a 914-6S.
All of this will make you car worth much more than a stock six beacue now you have a fun car with parts made by Porsche. I hope this is what the case is because I am doing this to my factory six very soon.
Can I get a hell ya?!