Power supply question for NEMA 42's

For those of you interested, with your help, I've made great progress.
The following is a little long winded, but I wanted to make sure I
gave the information you needed to offer me some advice.

Here's what (I think) I know:
X Motor #1 12.5 amps, .29 ohms, 3.6 volts
Y Motor #2 8.0 amps, .5 ohms, 4 volts
Z Motor #3 10 amps, .3 ohms, 3 volts
(because of inaccurate ohm measurement, motor #3 is worst case, but
may be same as motor #1)

I have decided (with much appreciated input from Tim to run 1/2
winding at 1/2 rated current or below)

I'm using a 34 Volt DC power supply to test this setup
This ranges from 8.5 to 11 times rated voltage. I can tweak this
supply to about 37 volts DC.

I have another transformer (which by changing taps) I can use for
57, 62 or 68 volts DC. At 62 volts DC, this will give me between
15.5 and 20.6 times rated voltage. By changing to the other primary
taps I can modify this a little up or down.

Any advice about what power supply voltage would be appreciated.

Now to a follow up question assuming I go to the other transformer to
increase the voltage:

I'm going to switch to all voltages being AC from now on so we don't
mix metaphors

My two transformers from the original Bridgeport NC power supply,
don't indicate a VA rating (consistent with the rest of the designers
philosophy), but do weigh about 38 pounds each, so my guess is they
are pretty substantial.

Originally the first power supply had a transformer with two 12 volt
secondary windings with each going to a bridge rectifier and then
running in parallel to the same capacitor. I'm guessing they did this
to increase the available current - each secondary winding would
handle half the current for the load. I'm now using the two windings
of the secondary in series for the 24 volt AC of my test bed.

If I change to the larger transformer, using the 44 volt AC
secondary, do you recommend putting the two secondary windings in
parallel on this transformer? I know nothing about bridges (other
than what they do). Some of the bridges in my old controller are
about 1" X 1" packages and the one that was originally used for the
12 volt (13.7 volt DC0 supply was made out of separate SCR's
connected by some pretty heavy wire. Am I safe if I use the larger
transformer in switching from the small bridge to this one (or is the
higher voltage likely to damage it?

Thanks in advance for your advice.
Jeff