It does look like nice horn, also like it came from two different bucks, but that is OK, unless you harvest it from the skull yourself you have to work with what is available.
If you are going to make a right hand knife I would put the bottom one on the left side. It looks like it will have the nicest grain and the owner will look at that side the most.
I would work them up, leaving them a little over size, then go to the dehydrator for a week or so, measuire them before you put them in the dehydrator and after a week, if they have shrunk, leave them in another week and see if they have quit moving, once they quit put them on the knife.
Brownells Acra glass is a good slow cure and will penetrate into the horn for good adhesion.