The engine isn't the concern - it's the transmission, rear axle, frame & hitch, brakes, etc. And you will likely exceed the limits of all of them.
You have the Workhorse W22 chassis under the Southwind, so it is rated for a maximum combined gross weight (GCWR) of 26000 lbs. That's the max weight for the motorhome and everything in it plus the Acura MDX and the tow bar. A 37 foot coach with the usual gear is likley to weigh in somewhere between 21,000 & 22,000 lbs, which means the MDX will likely casue you to exceed the GCWR. exceed the Also, the reciever hitch on the Southwind is rated for 5000 lbs max and the MDX will stretch that to the limit or beyond.
In short, you are really pushing your luck towing such a heavy vehicle.