Sheldon,
I'll urge you to call Dave Kiff again, just because he's a pleasure to talk to and so helpfull, not that anyone here minds helping at all, and likely enjoy it.
I guarantee you, he will make this all too easy for you.
This is what he suggested to me along the same line. The first (main body and neck)reamer, have it made with the neck and throat already part of the reamer, this will do the complete job on the shorter throat chambered rifle($135), the next thing you'll need if you want a longer throat, for a longer bullet or OAL on one of them is a seperate throat reamer ($66). That is about it. The dies will work with both, regaurdless of the cartridges OAL if the case itself is identical.
If one is a tight neck, needing turned cases, and the other is not, you can have Neil give you bushing for both neck dimentions and you are off and running.
If the necks ar going to be different, have Dave design the reamer with the smaller neck on the main reamer and tell him you need a neck and throat reamer in one for the larger neck chamber, cost is the same.
I'm not sure if you mean the necks will be different or the throat though. The throat just has the rifling removed for the length of the bearing surface of the bullet on the loaded cartridge, and the leade just tapers this into the rifling, normally at a 1.5 degree angle, where the ogive finally makes contact with the lands. You see, the "throat would have no bearing on the dies sizing the case, as it is beyond the chamber, starting where it ends.
Dave will have knowledgable suggestions as to what works and what doesn't and save you alot of headache durring the process I assure you. He is there to sell you the right tool and he aims to please just like a good smith, a super good guy.
It sounds like you are going to have a "couple" MORE nice rifles when you are finished here.
Good luck with your new toys.