2800 Caballeros compared to 21,500 El Camino's.. and from about 20 feet you couldn't tell the difference.
On the face of it, I'd say do what you want with it, and keep the ability to put it Back to stock.. (eg. if its got the 6 banger in it, take the drive train out and replace it with something fun, but keep the original drive train). If it was a SS/Diablo, then maybe it would be worth some more money, but the market isn't "VW Bus Shell for $5k, $20k+ for restored" hot for them, really.
WILL it be? Its anybody's guess. It is a beautiful car and looks in fantastic shape. I am over here in the same boat with a 86 GP. Im just going to run mine and if/when the time comes to replace the engine, move on to something fun like a 383 or LQ9 6.0. Until then, nothing wrong with running it and putting it in some shows as Stock.
You never know.. Someone might come along and say the right number to ya.. Everything on the planet is for sale.....for the right price. Mine is $10k for the GP. Someone pays me that, shes gone. Someone offered $9k, and that gave me pause, but I hadn't even had it 3 months yet... lol
Keep it, run it, do what ya want with it, IMHO..
-Gonz