Wheelbase has a big bearing on whether the tow vehicle can handle the sail area of the trailer so that the trailer does not control the tow vehicle. In this case the tow rating makes the wheelbase a moot point as nothing out there would be too long in that weight. There is a chart on many sites giving max trailer length for a given wheelbase. It starts with 100" being suitable for a max 20' overall trailer and goes up from there.
The OP is being wise to ask before getting anything to avoid the pitfalls that can occur without research. Unfortunately I don't know of any units that meet his requirement other than the Lance 15 footer that I think has a major flaw in its use of easily scratched plastic windows.
