Just one dummies’ opinion, but I suggest to you that you may not need any dies. 

I load a number of Maynard cartridges, and none of them get the modern normal, “size, expand, (charge and seat) then crimp”  treatment. First, Maynard cases in some calibers are very difficult to get or tedious to make, and working the brass by sizing and crimping will greatly shorten its life. 

You don’t need to crimp, as the cartridge doesn’t have to sit in a magazine and endure recoil. You may very likely be loading with black powder, and it does not need a crimp to ensure good ignition. 

What I do is fire a few rounds and measure the inside diameter of the case mouth. My goal is to find (or create) a bullet which will give me a nice slip fit into that case mouth. Sometimes I have had to order custom molds to get a bullet of the weight and diameter I want. Occasionally, I have used paper patching to bring up the diameter of a bullet. You and also swage out a cast bullet using a homemade die and an arbor or hydraulic press. 

Opinions will vary on this, but using soft cast bullets, I have had no issues using a bullet somewhat over groove diameter to achieve the case fit I want. 

Read the reproductions of the old Maynard catalogs. The loading tools they supplied did not work the brass at all, they simply aligned the bullet with the case and allowed a uniform seating depth.