The LT1 with highway gears and auto, in stock form is a bit of a dog, my 85 with a few mods will walk away from a LT1 in this form.
Or sell it on ebay and take a major hit.
Trying to judge somethings worth by ebay is a bit crazy, the same car could go up on ebay next week and not make it over 5k, the week after it might go for 17-18k. Ebay can be good for getting rid of something quickly, but not at premium price...then again, you could get lucky and get several people hyped up in a bidding war all determined to win and it could hit 20k. Not very likely, but that's just the nature of auctions.
As for LT1 auto's being dog's, I'm not sure what you consider a dog here, and I'm definitely not the fastest car, but mine with very few changes runs 9.0's at about 82mph through an 1/8th. I haven't ran a 1/4, but I believe that should translate into 13.9's at 112-114ish...like I said, I'm not the fastest around, but I'm not concerned about being the slowest either.