Northernlights, welcome aboard! I had to chuckle at your reply to Bob and Sheri! They were at the rally so maybe didn't have a choice but to tow in the rain. Likewise for us. We caught the Ivan residue accross Pennsylvania. You know that old saying about 'come h___ or high water'? Well we got the high water but that didn't stop us from getting to the rally!
We tow with the F350 diesel but engine, tranny, and rear axle are the same as the F250. You'll not have a problem towing it. The possible exception is 3/4 ton trucks **sometimes** need a little help with the rear suspension if the pinweight causes the tail to sag. Air bags will take care of that. But the 3400RL has a light pinweight so that probably won't be a problem. Just my opinion for whatever it's worth. As for towing in the mountains, the 6.0psd and torqueshift will have you smiling bigtime.