As the name suggests, this cocktail is dominated by amaretto, with lemon juice providing the sour balancing element and a slug of bourbon giving backbone
Switch simple syrup with some cherry syrup (if you have it) such as Luxardo Maraschino Cherries, it will be more complex. Amaretto pairs well with cherry.
I made two for a side by side comparison, one with Bulleit Bourbon and one with Tincup Rye. The rye won out for me. Both are very nice. My wife preferred the traditional (no whiskey). I preferred this but with rye.
I love how this recipe is still spectacular with a budget amaretto like Di Amore and a serviceable, if not stellar bourbon like Evan Williams bottled-in-bond. What balance!
Made many a batch of this over the years. Works great with a lot of spirits besides burbon.
Some notable ones are Aberlour A'bunadh, Goslings 151 and DonQ 151 (although in that case omit the sugar), and Chateau de Lacquy 12y.