Depends somewhat where you/the car are, but $40K seems a bit on the high side unless it is really nice, has some very unique options, etc. For that money I would get it on a lift and check the bottom closely for rust, damage, etc. Obviously not a "matching" numbers car but that isn't a huge issue (at least for me), but it would have be really special for me to pay that type of money. Yes there are some on here who will say that $40K isn't bad or isn't that much, well to me that is a pretty significant investment seeing that I paid slightly more than that for more 01 Viper GTS ACR (1 of 38 made) and about the same for a brand new 14 Ram 2500 (granted the truck will not appreciate like the Challenger, just a data point).
At the end of the say, it is your money and will be your car. If you have the money and the car makes your pulse race and heart beat faster, then go for it.