I've been called the "Weight Police", and flamed so many times for preaching to others to stay within their trucks GVWR, that I can't remember when it started. BUT, almost all anymore use their trucks RAWR...Now I don't, but we're not talking a very heavy 5er here, with a GVW of only 14,400#, and a possible pin weight up to maybe 2900-3000# and that's if 5er is loaded to it's max GVW, (I've never loaded a TT or a 5er to it's max GVW). A Dually, in my mind would allow for a more stable towing experience, especially if one is towing on roads that are mountainous and curvy, but the OP's 5er IS NOT that heavy.
Any of the Big 3's newer 1 ton 3500 SRW trucks should be able to tow the OP's 5er. and be within recommended specs. Might exceed GVWR some, but not RAWR.