The Titan is an excellent truck with a lot of power, hence the high conventional (non-fifth wheel) tow rating. However it is still 1/2 ton rated in terms of components. The rear axle, a Dana 44, has been problematic even for conventional towing, unless the gears are properly "tempered" under towing load. It is a semi-floating design, like all 1/2 ton trucks. A fifth wheel carries a lot of weight (20-25% of gvwr) over the rear axle and I would personally opt for a 3/4 ton with full floating axles which are a lot stronger design.
2012 Flying Cloud 23-D
1971 Safari 23 (sold)