Ours had a single large ram Morse Teleflex system, with the ram between the engines out of view. That is a long time ago though, and now I reckon you'd be much better served going with a Hydrive setup, it's very nice stuff made from nice quality materials and is designed to last, unlike many modern popular systems. http://67.18.218.201/~hydrive/
A single ram will do the job if it's set up correctly. A bonus with single rams is you don't get the creep that twin ram setups are succeptable to (when over time one engine starts pointing differently to the other, requiring a valve to be opened to allow you to correct it. It's all so unnessesary.)