When you visit a distillery they will only serve you two sips basically or about two half shots of alcohol in total. There are no full drinks and no mixed drink cocktails. Most people I watch take a sip of the sample and leave the remaining. So if one is concerned about driving over the course of a day you might be able to visit three distilleries max but realistically two, but in 8 hours time you will not come close to raising your alcohol level or feeling a buzz. I found that different than Napa Valley wine tours where I felt you needed a driver.
Heaven Hill and Willett are practically next door to each other in Bardstown. Maker's Mark and Jim Beam are short drives from Bardstown. Wild Turkey and Four Roses are close to each other near Lawrenceburg, KY. Buffalo Trace is right in Frankfort. They are all within 50 or so miles of Louisville.