Richard it's happened to all of us. Mine was a 59 porsche roadster type d convertible. 6500.00 I didn't have the cash, and had never applied for a loan for a car, so I told the guy if someone gets the cash first to you. sell it. An hour before my loan went through, he sold it for cash to a guy. I was bummed, esp now it must be worth 35k today. But it wasn't meant to be, and I would have been a poor owner, compared to what it deserved!(I was 21 at the time). I would never had the cash or garage to keep it protected from the elements, or spruce it up right. So it's the one that got away.
Those SS's are really nice, so I do know how you feel! But a 68 convertible is also nice( My brothers both had 68 Firebirds in highschool. One had a convertible with a 400 under the hood, the other had a hardtop with a 350.
Both sold for next to nothing back then.
Just think of the truck you want to start, the convertible...crate engines with obscene hp!