My 1936 (?) Craftsman 101.07830 12 x 24's ways measure 5-13/16 x 3/8" so I think the conversion MAY be possible. You'd probably have to reuse your compound as the 10-12" had a riser cast into the compound to bring the tool holder up into line with the higher spindle, as I understand it.
On babbet caps, I've not heard of a torque specification but that's certainly not to say there isn't one. I tighten them down until I start feeling resistance when turning the spindle by hand, then loosen them about a quarter turn and see how it runs. Several of these lathes I've had over the years would lock the spindle if the cap bolts were tightened to around 40 ft. lbs. or a little better. Using this method, I'll always mark the bolt heads with a silver Sharpie marker by running a single line from the top of the bolt down the side, over the washer(s) and just onto the cap surface. If any of the bolts move, it's immediately noticeable.