What road double cranksets will work with a 108mm JIS square taper bottom bracket spindle? So far it seems like the Shimano Sante or Suntour Sprint cranksets are the only ones that would fit my bottom bracket spindle (I am hoping to keep both BB and spindle).  Am I missing any possible cranksets?
Going off-spec here is only useful if your spindle is actually symmetric 108mm.  If it's older and asymmetric it may actually be equivalent to a wider modern bottom bracket.  You also don't specify a BCD preference; it looks like the cranks designed for narrower spindles seem to be 110mm BCD.

According to Harris Cyclery, the Origin-8 cranks give a chainline of 43.4mm with a 107mm bottom bracket, which would be only 0.4mm off the Shimano spec of 43.5mm if your spindle is symmetrically wider.

The Sugino XD Swiss Cross lists 45mm as the chainline with a 110mm spindle; that would be 43mm in your case and 0.5mm to the inside.  Possibly good if your frame can handle a narrower Q-factor.

The TruVativ Touro and other TruVativ square taper cranks also seem to be designed around a 108mm bottom bracket.