1969 plymouth cuda 383 4 speed $$$$ how much

Nice car. Great to see that they are still out there. I'd be curious to see how that car would clean up. My opinion is that to be "nice" it would need a re-spray. I'm not saying it can't be fun as is, or that I wouldn't want it in my garage.
As for value... I think it's rarity will hurt as much as help. Here is why I feel this way. A rare, original car deserves a higher price, and also, a perceived debt to the hobby to restore it to stock by most potential owners. In this economy, those willing to pay the premium for a car that requires a premium restoration (in attention to detail=$$) are in short supply. People just aren't spending. The missing fender tag is another deterrent.
I think it would be prudent of you to hold the car until you find the fender tag and wait for the market to return a bit. Just my opinion.