Replacement for original dual lead screw system. Except for printed parts (from this thingie) You will need:
1x ball screw SFU1204 540-550mm long with nut
1x nut/bed mount from https://www.thingiverse.com/thing:2896703 "1204SFU_simple_for_new_O_Tumanov"
1x E8 angular bearing or F8-16M thrust bearing (setup with thrust bearing is untested)
1x 6700 or 6000 type bearing (both optional)
1x 5x8 coupling
4x M4 screws for bed
14x M5x16 screws
If 6700 type bearing is used on top, along with this carriage: https://www.thingiverse.com/thing:1930233 print area remains unchanged. Using cooling fan mounted on the back (like in original D-Bot) and/or 6000 series bearing will decrease print area, or You will have to move bed slightly to the front.
Top bearing mount shouldn't be installed if Your ball screw isn't perfectly straight.
Engine is mounted on the top, so bed can go all the way down, if electronics & power supply are installed on the side.