When constructing an optimal bluffing range from weak made hands that you now want to turn into a bluff, is it best to use combos in the top of that range or bottom of that range (if you're not taking into consideration blockers and what not)?

I'll continue with a simple example...

We have QJ on a 3TJ45 where a backdoor flush was completed by the river. we want to turn QJ into a bluff and have calculated that we need to be bluffing at a 50% frequency. for the sake of discussion lets say we need 10 bluff combos. is it best to use..

a)10 combos from the bottom of our weak made hand range in this spot (J8, J9)
b)10 combos from the top of our weak made hand range (AJ, KJ)
c) doesn't matter. a random mix of 10 combos will do

thanks