[slowmover]

There's no "risk" in running 58-62. Big trucks run 62-66. A little above them, but below the idiots in cars is "the rocking chair". (That van won't stop or handle worth s%^* above 65). Mixing with cars means throttle changes, more steering inputs, plus brake use. All of those a fail.

Thus, need to analyze engine run time versus distance. And then look at travel speed. Average MPH will tell you best trade-off.

Get an engine hour meter

I've been running to customers for years. It isn't the travel speed, it's the road design and traffic percentage. Year after year the time won't really change unless one switches from daylight to dark (far less traffic = higher average mph. But night running has its own dangers).

What is open to manipulation is cruise control set speed based on average mph. There's a sweet spot on the graph where time en route vs fuel consumption meet. (Burning thru tires kills fuel savings; you are getting 70k plus from tires, right?)

The ironclad determinant -- as always -- is vehicle spacing. If one is ever surrounded by other vehicles, one has screwed up. Severely. The speed which allows consistent 200' spacing (minimum) out ahead, and if one drives otherwise to avoid pack formation around one, is what really finishes set speed determination. Safety, then fuel economy.

Find the averages. Hit the sweet spot.

As to towing, you didn't need a Class V hitch. Class IV would have worked. Just need to set up a weight-distributing hitch properly. (Leave van springs alone unless you're changing them all). Trailer tongue weight IS NOT the same as cargo weight. Use of a CAT Scale is key. Be glad to walk thru that. Better handling and braking is the result.

That crap out of the way, it's really impressive the amount of work you've done. I really like straight sixes. V8s have their place, but a big six is sweet.

Towing plus A/C use: HD clutched mechanical fan.

The downside of a straight six is weight. A lot of Iron to keep cool. I wouldn't screw with old school in this. In fact I'd get the radiator, fan shroud and fan from a big block van.

Then you can mess with thermostat temps.

I'd also add a second A/T cooler (plate and fin) downstream from radiator that will bypass cold fluid (B&M Racing). Centered low across rad face, but "within" fan shroud profile and out ahead of all else.

And a Derale power steering cooler. (Same).

Mount both with metal strap or similar. Not with zip tie to radiator.

Filters for each downstream again.

A bug screen also a good idea.

(You can see where big capacity radiator a better choice, now).

This is how we followed MoPar guidelines and factory build starting in 1960s. Just as effective now.

And it's "aero" as intake openings should "work" with all the other fine work you've done. I'm old enough to remember the heyday of vans. Things didn't always work on that score once towing was involved. Gotta have engine room airflow. Vans are sensitive to this.

To take it back to where I started (as this is the aero thread), a consistent travel speed -- verified by averages -- will put all other aero changes in proper light.

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