A fundamental component of your search is whether the car is a tube/space frame clad in metal or a true monocoque tub chassis. There are only a couple true monocoque based replicas you would encounter: Superformance (their car SAYs Superformance on it), ERA, or RCR. Each are very unique in their design and look. I am of course excluding a REAL 40 or a one-off built tub car such as Holman Moody, SAFIR or Gelscoe. Once you see one, you will know them in the future. You can search the forum here to see what each looks like. As for tube/space frame cars, there are several as well: GTD, Tornado, Southern, etc. Once again, these all have differences but HARDER to tell apart once they are clad in sheet metal (if they are). I believe that if you are in the market for a 40, you first have to decide if you want space frame or monocoque. Then look deeper into each manufacturer. And then even deeper into your wallet as the monocoque cars are higher in price (at least they should be) but now with prices so high, it is not uncommon to see prices sky high for just about any car. Any true owner should know what the hell their car make is and be honest about it. Once again, with the market where it is, I see people selling cars and have zero clue what make it even is.