It would not be possible to use them for Conquistadors as their timeframe is very firmly Medieval - I reckon the latest you could get away with is mid to late fourteenth century and even then they would be looking fairly archaic. If you haven't already done so look at the figures by Revell and Caesar of Conquistadors and you will see that by the 16th century the whole style of armour and clothing, and the bows themselves, had changed. As you get later on in history the rate at which clothing and armour changed seems to accelerate - when you think about it a Saxon fyrdman at Hastings probably didn't look that different to a guy who was fighting Viking raids two centuries before but if you compare a mid-sixteenth century Gendarme to a buff coated cavarlyman of the English Civil War, less than a century late and there is no comparison.
One better option to reinforce your conquistadores crosswmen can be the italian crossbowmen included in the Italeri "Hundred Years War French knights",they are late XV centruy, quite fine for beggining of XVI c. as well.
I suggest as well to use the men wth crossbows from Miniart (burgundian archers and some french from assault ladders and ram), you can even convert them with some genuine spanish heads from revll or caesar (or even the helmed heads from A Call To Arm english pikemen)