Rick- I re-did all the systems on my G-Cat a couple years ago, and those are the exact blocks I used for the Jib Cleats. I also have Ratchamatic Jib Blocks for increased holding power. I put together the 8:1 mainsheet before they sold it that way- had to bolt an eye-strap above the cleat with an extra block on it, and tie the bitter end of the line right through the open center of the block (the 8:1 system they sell has a becket over the center pulley on the base block to secure the end of the line.)

It's an $81 difference between the carbo-ratchamatics and the normal low-profile 6:1 system. Something to think about.