you can probably leave the cups in the frames they are already in, and let the captured bearings travel with the fork to the new bike.
as for making trusses from 5/16 brake line, I squeezed the axle end in a vise and then finished hammering it flat on the anvil portion of the vise. Then drill a hole for the hub axle. At the headset end, there are various ways to attach including premade yokes, or home made yokes. You can also tap the inside of the brake line and get just enough threads to bolt to the yoke. Don't torque too hard though, it's only about a half of the needed thread height.