I tow my 39 velocity with a 99 3500 dually with the 6.5 diesel. I love it. Gets around 9.5 to 10 mpg and absolutely no problems. I have a problem running down the interestate under 80 or 85 mph though. I cruise at or above 85 mph. I had heard a lot a bad stories about the 6.5 but mine has proven to be quite a work horse. It has 88,000 miles on it, but service it every 2500 to 3000 miles because I only use it to pull my boat. I can pull with the best of them. On a recent rainy day I went truck shopping to kill time and drove the duramax and the 6.0 ford diesel. Both are power houses. I like the 6.0 but I read on the ford forum online that there are still some problems with these engines that will be worked out by the 04 year model. An engineer also said that they are reworking the fuel rail to eliminate the past problems which will also make the engines as quite as the duramax at idle.