The Rock Solid scope mount showed up. It's a substantially beefier piece than the pictures imply. The only problem is the large CNC'd advertising on the side. Not as bad as the Texas Weapons System AK scope mount, but big enough that "fill it with Bondo and then Duracoat it" just went on the Mosin to-do list.
Next step is to order a new firing pin and cocking piece. I'm going to skeletonize them to reduce the lock time, and discard the safety knob entirely, which will mean coming up with some other safety arrangement.
Purchasing the scope has moved further down the list. I'm still sussing out all the reticle and focal plane stuff, and it looks like a decent stop will be twice as expensive as any other single part, including "rifle, one each."