I am installing a Merlin KSU (model unknown). Do Merlin systems have a standard wiring configuration for all types of KSU's? The existing cables wire out on a 66 block in the phone closet. The jacks are Leviton Cat5 568B style. What is the best way to convert the 66 side to the modular jack on the KSU?

The best way is to punch down your 4pair to
the 66block and put a 4pair mod end on the other end and configure it as a 568b also. then just plug it in to the system.
Hope this helps
dtmf

If you're not sure how to lay down the mod-end, compare it to a cat-5 patch cable. Or (this may be a little pricey), cut off one end of a patch cable and lay it down on the 66-block. Match color for color. Plug the other end into the system port.
Also - there are RJ45-66 adapters that slide right on the 66 block. You'de then take a patch or 8-cond straight-through cable from it to the merlin cabinet.

>Do Merlin systems have a standard wiring configuration for all types of KSU's? <

Yes they do!
The Merlin is in a world of it's own, when it comes to wiring, I always had some one else do em cause they always ate my lunch, could never get em right. I ended up having to make my own cords straight from the Key Unit.
Good luck