Sweet deal! Congrats on the Two Spools!
The Two Spools takes a standard needle, 15x1.
To treadle that machine, you will need a cabinet. Finding the right National or Eldredge cabinet for a Two Spools can be a bit difficult. The machine head only fits into a certain cabinet top.
I once had my Two Spools in a Singer straight-leg treadle with the cabinet having an modification. Here is the link to that simple job:
http://color-my-world-with-warmth.bl...two-heads.html