Before you start this operation, you want to look at several important considerations other than the lock plate covering the existing lock mortise. 1st locate the middle of the pan on the existing vent hole, now check to see if the lock plate will cover the mortise. 2nd check to see that the sear will engage the trigger at the correct location. This is very important to have right, or you can end up with a non-functional double set trigger, or a very hard pull on a simple single trigger. If you don't have the new lock in hand to check these measurements, you can cut out one of Track of the Wolf's full size photos from their catalog. A measurement from the center of the pan to the sear will help to quickly determine if your proposed lock swap will work. I think that L & R makes a replacement lock for the Hamm and similar sized locks, you may want to check that. The Late Ketland lock is a superb lock, but may not be an easy fix for your situation. If you are set on the Late Ketland, you may have to panel the lock mortise and move the triggers...
Bet I scared the h---- out of you, but better to be sure before you leap...
Ron