Are you able to install both of them separately? If you are, then near the beginning of the Gulliver thread top post is a little section called "Little Blocks users" with links to the older versions of Little Blocks & SlimevoidLib that you'll need to play with Gulliver. Pop those Little Blocks and SlimevoidLib files into the "mods" folder, start up your Gulliver Forged profile for 1.6.2, and enjoy. (You may need to move any existing mods out of the "mods" folder that aren't compatible with 1.6.2, otherwise it'll crash.)
Reply if you didn't understand those instructions, especially if you've never installed either mod before.