A good question because 4R Yellow Label has a distinctive taste, one that doesn't really mix well, whether as opposite or complement, with the bourbons of other companies.
As I result of this, I generally will blend it intramurally so to speak. I just added some 4R SB to a bottle of 4R Yellow Label and it made it stronger and richer but preserved the signature floral character. (Any 4R SB will do I find, it doesn't really matter which, they are not that different). Mariage and its brethren will work too but you get more oomph from the SB.
Here is another way: blend it with Bulleit. Bulleit comes from some of the same bourbons in 4R SB. It's all of a piece. So 1:2 4R Yellow Label to Bulleit and you get a still potent whiskey with a lot of floral and yellow fruit character.
I don't want to rule out non 4R bourbons for the blend, I'd have to think more about it, but the above is generally what I do and the results are excellent - for drinking.
Gary