Originally posted by InitialD
Yes. 
Just mount the spurs onto the 705 oneway 1st gear oneway hub and the 2nd gear aluminum hub.
In fact, you can take the whole 2 speed gearbox from the 710 and fit it on the 705. Just make sure you use the correct aluminum spacer at the back of the 2nd speed aluminum hub. When you do this, make sure you use the 2 tension springs in the clutch shoe from the 705 one and not the one that comes with the 710 because the 710 is much softer and will cause improper and earlier engagement in the 705.
You may need to do some dremelling in the engine mounting holes on the chassis of the 705 so that the engine mounts can go further slightly to the rear to mesh the spurs as the 710 spurs and pinions are slightly smaller in diameter.
You can also use the 710 purple engine mounts on the 705 chassis. They are the same except the 710 ones are 1 mm lower. 
The only drawback is that the gear ratios of the 710 are different. So you'll have to use different pinion/spur combos.
Using 18/60 and 23/55 when using the 710 gears on the 705 wil give you the same rollout as 15/50 and 19/48 with the stock 705 gearbox and clutch.