Green Guard,
BEST RANGE speed DOES increase in a headwind.
The reason you will sometimes REDUCE speed in a head-wind is because you were planning to fly at a speed HIGHER than nil-wind best-range in any case.
For example, best range in something like a Barron might be around 130kts IAS at say 40% power- but nobody operates at that speed, as the increased fuel-burn is worth the faster speed, so everyone, in normal ops, goes for 65-75% and 175kts.
Now throw in a headwind that means range become critical- sure, NOW reducing to 160kts IAS at 55% will increase range over a normal cruise, but it is still faster than still air, max range cruise.
In jets, we DO always operate quite close to min-consumption speeds, as jet fuel is a very major percentage of overall cost and- hey presto- the FMC schedules higher speeds in head-winds and lower in tailwinds.