Is it for competition or for field use.

Going to be a shooter, field use.  Bent Ramrod 😲.  Nice solution!  David

Breech face must be square to the barrel axis for best accuracy.  Creighton Audette proved this conclusively many years ago.   

Stevens 44 and Favorite breechblocks must clamp up against the barrel face when closing.  Less than zero clearance.  At the same time the rear of the breechblock must be in contact with the shoulders in the frame, so that the rearward thrust isn't all thrown onto the pivot.   I can elaborate, but it's too much for a forum post.

What the breech block clearance is isn't the whole story. What it is with a case chambered is the rest of the story. I've owned single shots that appeared to have pretty fair headspace on an empty chamber. But chamber a cartridge and check it again, and the headspace is perfect.

Would not the face of the rim being in full contact with the rim recesses cut depth not actually be the actual determining factor for the actual headspace? 

Well, here's another take on how to headspace a high wall and it will contradict what some others have said here so take it for what it's worth and study all the ideas and make your own choice. My understanding of the Winchester high wall is that the breech block was designed to go over top dead center and then drop back down a little bit. The timing of this is not controlled by the curve of the lever bottoming out against the lower tang. It is controlled by the flat portion of the lever bottoming out on the two little tabs at the front of the lower tang. You should always want your breech block to go over top dead center and then drop back down. That way you're firing pin will always hit the primer in the same spot. Ultimately it's going to come down to how you're going to headspace the rifle and choosing your brass. If you're going to have the barrel against the breech block with minimum clearance, then your rim depth will have to be very close to what the thickness of your brass is. You could also give yourself more clearance with the barrel from the breach block and have the rim of the brass stick out slightly from the end of the barrel. In either case you have to take into consideration the rim thickness of your brass. All brass rim thicknesses are not equal even within the same brand . You may find the action may close easily on some of the brass but others bind tightly at the top when the breech block has reached its max but it may prevent it from dropping back down over top dead center. If you really want to look for perfection, use minimum headspace (around .003"-.005") and then trim all the rims of your brass so that their uniform in thickness.

My error by not knowing what it was actually that the OP was going to use it for. 
If replacing a barrel one can actually make it a perfect world if one is actually doing it themselves.
With that being said Ole Win did point out several real good points. 
And we actually did not differ very much in our two own individual approaches.