I'm in the process of purchasing a new (to me) toy hauler and it doesn't have A/C, it is however framed and wired for one. It's a 37' gooseneck with about 7' ceiling. What size unit would work best? Would two small be better than one large? It has about 21' of cargo, but it is not separated off.

I'd pick up 1 15k unit, look around they can be had for under $800. It will runon a honda eu3000i genny. My unit is 41' and 15K works great, I would add a 9k unit to the toy box next time just cause it is a seaperate area.

Great price on Colemans from place in Houston ,PM me.
I installed one in 32ft. cargo trailer, works great, easy to install.

I've got a 15k Carrier A/C on my 36' GN race trailer and it works fine for me. On really hot days, I have to keep the rear door closed and use that hanging plastic on the side door though or it can't keep up.

It's got a 5k gen so I'm not worried about power, I just didn't want to stick the wrong size up there and pay for it. To big wasted $$, to small and it won't keep it cool when it's 115* out.:)
Thanks!