The kickdown lever at the transmission should be all the way toward the front of the car with no throttle pressure... AND all the way to the back at full throttle. This is where the Lokar units have trouble. I have an Edelbrock carb and Lokar cable, and the cable travel at the carb did not match the amount required at the transmission to use the lever appropriately. If I set it up for full throttle, shifts came in very late. If I set it at 0 throttle, shifts came in early. A Holley will be different, but this has bit numerous people.
I ended up drilling the transmission lever and moving the attachment point for the cable toward the pivot in order to get the throw just right. It took some measuring and trial and error, but it works now.
There are two other things to keep in mind: There is a little slack in the kickdown lever inside the transmission. This generally goes away with the car running. If you're exploring this under the car with the car off, make sure you push the lever all the way to the front before measuring. You should have at least a 90 degree swing on the lever front to back.
Second, the factory linkage would actually push the lever forward when you returned to 0 or light throttle. The cable cannot do this. Therefore, it's a good idea to add a spring down at the transmission (a light one) to pull the lever back. The friction in the cable can really add up, and doing this helped mine behave a lot better.