Regarding the Sherline carriage lead-screw issue, when I started taking it apart last night I discovered that the issue went away when I took the hand-wheel off. Upon closer examination of the hand-wheel and the lead-screw shaft I found a nick on the face of the hand-wheel and a burr on the lead-screw. The burr on the lead-screw was caused by the grub screw, but I've got no idea what could have caused the nick on the hand-wheel. I stoned off the raised areas and when I reassembled things that particular problem was gone.
I've been plottin' & conivin' for a while as to how I can adapt the Frankendiff into a powered steer axle. Blender's build of a 1/14 scale TH407C telehandler gave me the idea I needed. He used Losi CVD front axles to build his steer axles. Since I've already got a butt-load of the WLToys 12428 replacement rear axles I decided to get a set of replacement front axles to see if they'd be usable. After doing a little (very rough) 3D modeling, it looks like things will work out. They both use a ball and socket joint in the knuckle, but the Losi uses a CVD joint while WLToys uses a CVA joint. A CVD joint has the ball on the axle with the socket on the half-shaft. A CVA joint flips that around and has the ball on the half-shaft with the socket on the axle. Here's a picture of the WLToys CVA joints.
At the top is the assembled CVA joint, in the middle is the axle with the socket, and on the bottom is the half-shaft. At the left is the dog-bone that would normally attach to the front diff. This 14mm section on the left is totally useless to me, I only need about the last 25mm on the right. The center section of the half-shaft currently has a 3.18mm OD. My current plan is to turn part of the center section and part of the tapered area just to the right of it down to a 3mm OD. This will then be Loctited into the outboard end of the modified donor axle, just like I did when shortening the donor axles for the rear diffs.
Edit: Due to the black finish I was worried at first that the axles might be hardened. However when I checked them with a file I found out they aren't. The dog-bone section was easily removed with a hacksaw.