In the vanilla version, killing giants gave Greater Souls. Now, you can fill up your Grand Soul gems by killing giants.

This makes grand-soul-hunting a tad easier.

I've done this by simply increasing the level of giants from 32 to 40. This "might" make giants tougher to kill, but I faced no problem with it.

Installation:
Drop the giantGrandSouls.esp in your Skyrim/Data folder.

Uninstallation:
Delete the giantGrandSouls.esp from your Skyrim/Data folder.