Michael -
Well now I'm really going to make you dive deeper into the rabbit hole. I originally made this beer when I was a professional brewer. It all started with us brewing our annual Grand Cru (30 barrels, or approximately 1,000 gallons) with a Chimay/DeKonick/Chouffe yeast blend that we got from the Brewing Science Institute (an INCREDIBLE source for yeast, but you have to buy a minimum 1 bbl pitchable quantity). I know I originally stated that we brewed it with Chimay, but I dumbed it down a bit. Now you're getting the full story. So anyhow. My assistant at the the time had a friend that he went to high school with who's family owns Justin Winery. He went up to San Luis and got this barrel. We acquired this barrel about 1 year prior to making this beer, and had already made a Kriek (for this one we took 50 gallons of our Jeremiah Red that had already fermented out and merely innoculated the barrel with it) that won a gold medal at the LA County Fair (funny story on that one, we beat out Samuel Adams for their "Cherry Lambic"). When we were done with this beer, we merely gave the barrel a hot water rinse (150F) and sulfur stick then bunged it and let it sit. When we were ready to put the Grand Cru in it, we just gave it another hot water rinse (160F this time) and put the beer in it. Since the barrel had already been innoculated the brett and lacto and pedio took right off. Twelve months later I was no longer working for BJ's and making grape juice concentrate instead. When I went back to visit 6 months later my former assistan, now head brewer, presented me with a 5 gallon keg of it that he had racked off. So now this keg has been sitting and aging for the last two years. After we started blogging about this, I went and tasted it. It is absolutely ready, and currently being carbonated so I can have it ready for my birthday party in a week. Thanks for that by the way.
Anyhow, I'm done being long winded.
Long story short, I wouldn't put it in a barrel with that much headspace. http://morebeer.com/search?search=oak+barrel ; Check that out for smaller oak barrels. That's going to be your best bet. But beware that once you inncoulate it, it's brett forever, unless you have it broken down, scraped and refurbished. I would also reccomend that if you do buy one, to put it through it's paces with a few big beers (Imperial Stout, Barleywine) first to remove some of the oak flavor. The oak is VERY strong in new and refurbished barrels. I've also found that beer only needs 3-7 days the first time you use an oak barrel. Good Luck!
Darin