Nice looking project there :D
If you have a device to measure the resistance, then the hotter pickup will be the bridge one. (Off hand I can't remember the numbers, but I'm sure someone else here knows.)
Otherwise, you said the set was secondhand? Then whoever sold it to you MAY have snipped some of the excess wire off so it would fit in their guitar; if thats the case, it's likely the bridge will have less wire than the neck, but this isn't really a sure way to check. Your best option is probably the first one.
Best of luck, someone else can probably provide more info. I have a set of MQs myself, I'm in love with them :D
EDIT: Hahaha, well at least that was easy :p Keep us updated on the build!