i don't "tow" heavy per say.but this should still help;
my truck (in sig) weighs about 8100lbs empty w/fuel and no passengers.
i carry regularly 2-3 ton on the back.i tow regularly a 1 ton lb chipper.
so im at 14-16k total very,very often (as in every day,to every other day often.this is a 100% full time use business only truck.-tree service.)
im running the dual ford windstar fans and they are pretty much overkill.
when on high,they will cool from 240 (if i let her get that high) down to 210 in 85 degree Maine summer temps (like now) inside 1 minute.
they don't need to come on very often.
pretty much only;
when the A/C is on.
when driving under 40 mph (for sure 25 mph zones creeping through towns)
and when going up a nice hill with a load on her.
no complaints or issues here,other than i can't wait for my variable rate controller to arrive,so the things stop cooling me off so fast.i don't like the fast temp drops.need to tone it down a bit.
however! these are not overkill in the winter when the plow is on.they're pretty dang near perfect then.
well maintained coolant system.
ready rad 3 row brass/copper radiator.(worked fine with the stock 4 row too of course.but it got so old and was leaking in a few spots.)
external add on coolant filter.
stock motorcraft 192 degree T-stat.
fleet charge coolant premixed with SCA's 50/50 with distilled water.
13 lb cap.