Sealing milk bottles?

[brazenheadbeer]

I have quite a few milk bottles. I think the opening is about 1 1/2 inches. I'm looking to age some bourbon in them.

Can someone suggest a way to seal these? I'm wondering if I should use a oak dowel but I would be concerned I would bust the bottle driving the plug in. How about cork? Any suggestions?

Here's what they look like...thanks!

http://www.enasco.com/product/C19156N" onclick="window.open(this.href);return false;" rel="nofollow