Contemplating a couple of Mauser builds..... Wonder what kind of scope mounts I can use that dont cover the crests and don't need holes d/t through the crests?

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Option one; Griffen and Howe or EAW side mounts. (NECG has them)
Option two; Recknagel barrel shank claw mounts. (Reck catalog page 33)
Option three; Custom base milled into the barrel shank, from the barrel blank.
Option four; LER or dot sight/ scope up on the rear sight base.
The problem/issue with a base up on the barrel shank is that your ring has to grab the front bell; those are hard to get. Recknagel has those. Other option is to use a straight tube scope, like a Leupold 1-5 or such.
Option one is easiest. Option three is classiest and most costly. Option two is, well, in between. Option four is not classic in looks or function. Depends on how much money and effort you have.

I'm going through the same sort of design process currently for a Mauser Kurz.

Here are the latest set of thoughts I've passed to the "smith, he hasn't agreed to do it yet but its about the 3rd or 4th idea we've discussed and I think we are closing in. My rifle build is somewhat simplified in that I have decied to use Kahles S2, in that range (from the 1960's) there is a fixed 4x and a 2.3-7 that share the same critical dimensions.

"So I’ve been think to try and define what my objectives in mounting the scope are:
- to not drill and tap the action, and not to place anything on the receiver ring
- to be able to change out the scope easily (these old scopes fog up sometimes) and this is a rifle I will hunt with often.
- to preserve the integrity of the rifle as much as possible retaining sympathy with the past but as far as possible ensuring it is a useful hunting companion.

As we’ve discussed my first plan was to have custom bases made that would take Conetrol rings. These have the advantage that they are adjustable for windage. However they fit into a socket and I recently saw pictures of a similar sort of installation on a high end rifle , the “removed” look of the sockets is not good.

So I am very much in favour of your idea that it should be a ring on the front bell of the scope so that the front base is on the barrel reinforce, since we do not have the expertise to disassemble a scope to solder on half rings and we don't know anyone here who does, we need to come up with something else. I’m not prepared to spring for claw type bases, apart from requiring a lot of money, in my experience t these are seldom successful in our rough NZ conditions.

So I have another idea, I like Talley dovetail rings, especially the older one screw at the top joint type, set enclosed, these are actually for a small ring mauser.
What If you were to make a custom rear base for a Talley ring, after the fashion of the Dorlearc one in the photo attached. For the front, add a saddle with a transverse dovetail to the barrel reinforce. This front dovetail would take a slide with a Talley dimension dovetail at the top - like some claw mounts do.

A Talley ring would have its “ears” cut off, be re-contoured and a new ring soldered on to take the scope front bell, if transverse screws in the lower part of the rings base were beefed up a top split might not be required. The height of the slide would be made to suit the difference between the 26 mm rear ring and now 36 mm front ring.

Aesthetically maybe this could be a bastard orphan, neither European or American, and too "modern". It does meet my objectives to be removable, allow the scope to be switched and is strong and neat"

Sure you can make a front ring based on a Talley system by soldering (I would weld it) a new ring onto the Talley or Warne bottom. The Recks are clamp ons; they all are not solder on; that doesn't work too well on aluminum scopes. Then you would just have to drill or solder on, a base on the bridge. Or weld on a square bridge dovetailed for the TAlley ring.

I have an original 1906 J.P.Sauer & Sons, marked 30 USG 1906, all all parts in it are serial numbered to the gun, and its not drilled and tapped but has a receiver sight on the bolt release, and the sight slot in the rib was installed by JP Sauer..The mod. 98 action was actually made by J.P.Sauer, the screw slots are tight and positioned North and South, and its in mint condition..I hunt with it, and would love to scope it, but It would ruin the gun to do so, and I would have to install a new bolt handle. I have wrestled with this for years, and I can't change the gun, so I just hunt with the iron sights, and its a joy to do so....

My point being go ahead and drill and tap it for Talleys and make it scope friendly.. Covering up, drilling and tapping in the emblem is done on most ever custom Mauser out there, so unless you have a very valueable and rare collector, just scope it.

The only other option is a Griffen & Howe side mount, or a Jaeger side mount. However, in many cases side mounts can hurt the value of the gun if its collectable, and patched holes in the action can really devalue a rifle.