Parabee has the Magnequest TFA-2004 output transformer which has single taps and can be switched with a single-pole, three-throw switch. The Paramount upgrade transformer from Magnequest has only two taps, and a single-pole, double-throw switch will do the job.
The stock Paramount output transformer (shown below) has two tapped windings which are wired in various combinations of series and parallel to achieve the impedance changes, and it requires a two-pole switch. In the one that I modded, I used a 4-pole switch (actually a Foreplay input selector switch) with paralleled poles for lower resistance.
Incidentally, the new Stereomour has a slightly difference design, and a pair of DPDT switches is the most efficient method; it can provide 2, 4, 8, or 16 ohm outputs.