Hemling wrote:
From parking in truck stops, I know I'm a little longer than a 53' semi trailer. Probably about 55-56' or so. That's plenty. I'm concerned with getting the new truck with 20" or more wheelbase than my Excursion and pulling my TT with it for a few years until we get a FW.
This is a slightly different question than where you began. Wheelbase (the distance between your axles) can give you a sturdier feel. On the F350, the difference between the two beds is 160" vs 176", or 10%, but I've never heard anyone complain about wheelbase as an issue with the F350. Considerations are usually more based on vehicle storage, room for gear, etc., as has been mentioned above. If I were in the market to tow a fifth wheel, the 16" difference in wheelbase would not be my deciding factor.
That said, this second question is not one of wheelbase, but one of total length. The short bed F30 would increase your current total length by 23", the long bed would increase you by 39". On this, I stand by my earlier comment - in the scheme of things, when discussing a set-up that will be upwards of 60' long, I don't think you are going to notice an extra 16" as a particular difference as you are headed down the road.