There's no right or wrong way to put the pickups. Mind when most people go with the 81/85 combo (or in your case the 81-7/707 combo) they usually have the 81 in the bridge and the 85 in the neck. I've swapped them around on a guitar(85 bridge, 81 neck) and everyone so far seems to love it backwards when I compare it to a standard 81/85 setup.
Basically what you get if you do it backwards is a
bridge pickup with more Growl than Bite (ie. More bottom end) and a
neck pickup that really cuts through(not as warm sounding, but definitely a lot more note definition). Try it, if it doesn't sound as good as you would like it you can always reverse them back.
(You may have to check to see if both your pickups use the Quick Connect cables. Some of the 81-7's and 707's that I've had to install previously were hard wired.)