Appears to be a #5 that has been milled to an octagon top. Here is a #5 that has been contoured to a #1 sporter with the bottom tang extended. Still needs the stock flange contacts squared.

If I remember correctly, Higginbotham sent my wood to Treebone and said that it was because it was a military action.

With your objective of a Custer tribute rifle, I'd go .50-70 instead of 50-95.  Three reasons:  First: The larger diameter of the -95 will make it harder to get the cartridge to clear the hammer and block and chamber right.  The 50-70 will be slightly easier, but not easy.  Two, the -95 has much less of a rim.  This will make it very easy to over run the extractor on a rolling block, and jam a loaded cartridge in front of the extractor.  Real pain to clear.  Third, the 50-70 brass is much better brass.  Disclaimer here:  This isn't in my self interest to say this, but Starline 50-70 is much better than the available 50-95 brass, which I sell.  The 50-95 brass has a very thin neck, and it's delicate and doesn't last a lot of loadings.   

If I was going to build this type of rifle, I'd chamber it in 44-77.  Smaller case and bottleneck makes it much easier to feed.  Good solid rim for the extractor.  Good durable brass at similar cost to 50-95.  I sell this brass also.   

As Kenn said, .30-40 and .30-30 would be good candates also.  As would 38-55.  the 8mm Lebel isn't real easy to get brass for.

The Starline 50-90 brass is great for making 500-450 #2 Musket. Just run it in the sizer and trim it to any length necessary. If you're just going to throw it away throw it my way.