I've been towing my 32' Crossroads Bel Air for a few years now with my 2005 Chevy Express 3500 van. I have the 6.0 L with the 3.73 rear (7700# capacity) and my TT weighs 5700 dry so I think I am in good shape weight wise.
I never had any real issues at all, I have recommended this van for towing to many people of the years.
This past weekend, we were towing from Baltimore to Raystown Lake. We followed google maps (bad call) and found ourselves on some pretty steep, winding uphill grades. On one, we were behind a school bus and never had a chance to build up any kind of speed.
Towards the top of the hill, my temp guage started to move up quickly, eventually triggering the "check dash guage" warning chime and light just as I was able to reach a pull off spot.
I put the van in park, cranked the heat, and in a few minutes the guage returned to normal and on we went.
I noticed the remainder of the trip that we had to do crank the heat proactively as we went up any kind of hill with a decent grade or length to keep the temperature from spiking again.
We took a better route home, avoiding many of the hills, but we still had problems on the hills we had to climb.
I also felt like I had a bit less power than normal, but I may have just been overly sensitive to what was going on.
Check for a lazy O2 sensor. It can be in spec enough to not turn on the check engine light, but cause the van to run with a slightly out of whack A/F ratio which can cause heating issues and low power.
Also, when is the last time you cleaned the radiator out? Bug guts, dust, and debris eventually clog it up. It might be time for it to be removed and cleaned. Also check the inside of the rad. Drain a little coolant and check that the tubes aren't clogged with scale.
2010 Cougar 322QBS 5er
2007 Dodge 3500 SRW Megacab, 4x4, 5.9L Cummins, 3.73, 48RE auto HYPERTECH MAX ENERGY or DIABLO PREDATOR tuning MBRP 4" Turbo back Scangauge2 for Boost, Coolant temp, Rail press & Trans Temp
Torklift Stable Loads