Hi, blu.
As you already know (I hope
) the 4R has been around for a long time, and it's had several major re-designs. The newest, 2009-11, we call "Generation-5". I'm pretty familiar with previous version, 2005-2008, having owned two of them. (The first, a V8, was destroyed by collision from a man who died at the wheel of a large delivery van. The 2nd, a V6, is our current Trailmanor TV.)
So they call mine "Gen-4". The previous version, from about 2001 (???) to 2004, is referred to as "Gen-3", and you might be shopping in that marketplace. I've not looked at the Hitch Receiver in those years; so, although they're widely used used by TM owners, it might be less "beefy" than mine. But in Gen-4, I know them both very well- and, per my two vehicles (V8 R.I.P. and current V6) I've actually owned and towed my TM with both the "heavy duty" and "standard hitch receivers!
The less ostentatious "standard" hitch receiver is actually very,
very strong. One pair of bolts, goes upwards, into the bottom of the box frame, and another pair goes sideways, into the tall side member at the rear. There's lots of steel, with extra "bulges" to reinforce the shape - and the steel is just as thick as the frame itself. And so, even though Toyota wants to sell the big "square box" hitch as an Option, I don't think that it's appropriate on the 4R. (Toyota does make bigger vehicles, like the Tundra, in which the "heavy duty" receiver is useful.) But in the 4R, I think it's overkill, unnecessary- you'll exceed other limitations of the vehicle before you exceed the capabilities of the hitch receiver.
So- if you're shopping within Gen-4 model years, I recommend that you allow both. Limiting yourself to only those vehicles equipped with the "heavy-duty" option would eliminate tons of well-qualified vehicles from your shopping consideration.
BTW, the 4R never feels "5000 lbs" or "4000 lbs" or any other actual mass of the towed trailer. It feels only the load on the hitch (dead weight and torque, and resistance to changes in momentum). So it's really only a suggestion-- if you drive a 3500 lb trailer really badly, trying to stop on a dime and accelerate like a cheetah and turn corners like a jack rabbit, you can get into plenty of trouble already. Drive smoothly, and stay keenly aware of nearby idiots on the roadway. In deciding where to put your stuff, do this:
(1) NEVER exceed a tire rating- try to have a comfortable margin.
(2) NEVER exceed an axle rating.
(3) NEVER exceed a GWV.
The 4R has a very limited payload before exceeding GWV. After you fill it with gas, sit in the driver's seat, and seat your passengers, snacks, etc., you won't have a lot of capacity left. And so, with the 4R, unless you're getting an older TM model with the 3500lb axle and 14" tires issue, I'm recommending that you plan on loading your TM more, and your TV less.
Towing with Toyota 4runner V6
which "generation" of 4R? Standard hitch is OK in Gen-4 models.
Linear Mode
