If you're going to lay out some money, look at item C on this page from the Murray catalogue. You save some money getting it all in one and it's easy to mount. Cheek blocks and a pair of doubles will give you 8:1 or a double above with a single cascade to double that would yield 8 as well.

Shop around for best price or buy it from Rick and support our forum GrandMaster.

http://www.murrays.com/archive/26.pdf