Sometimes, only two bourbons will combine in a particularly good way. I bought recently 4 pints of Woerner's Kentucky Straight Bourbon, a 4 year old (or more) private label out of San Francisco from 30 years ago. Each of these is slightly different. I took one, flavourful but almost too smooth, and combined it 50/50 with some current Old Fitzgerald 1849. The Fitz has good cereal and other flavours but is a little prickly on the palate.
The combination makes the Fitz glycerine smooth but adds its wheaty accents. A four grain perfect for neat sipping sans ice.
I'd be interested in any other successful two bourbon (and/or rye) vattings.