Knowing what I know today, there's a few things I would upgrade an Astro/Safari van - for Towing even utility trailers. They are:
- Install AUX tranny cooler. If pulling a loaded 3,500 lbs trailer (including weight of trailer), then go with an LPD Design cooler for 4,000 lbs. If pulling a 5,000 lbs trailer (including weight of trailer), then go with LPD Design for 5,000 lbs trailer. If one installs too large of AUX cooler, it blocks air flow into normal rad and AC rad. Thus, increasing their cooling down efficiency. Also, I'd go with LPD (Low Pressure Design) Aux tranny cooler. They problem best winter warm up and summer cool down ability. For LPD sizing, go with total combined vehicle and "average loaded" trailer weight. For more details, surf: http://www.transmissioncoolers.us/Merch ... -cool-thin
- Install Class III hitch that is "square bar" design. Thus, allowing one to connect a WDS to it - if you need to in the future. A few years back, I installed a Class II hitch on my Safari van. Two years later, I had to replace with a new Class III hitch. Lesson learned the hard way.
- Install Timbren SES units on its rear. If wondering, Timbren are like air bags without pressurized air inside them. Thus, no worry about future air leaks. And, they do NOT impace unloaded ride. For more details about Timbren SES 2,000 lbs units (which create more "weight support") assistance, surf: http://www.timbren.com/ses-van-suv.htm
- For towing, I hear that "Bilstein Shocks" are much better then all others. They hold more down pressure movement, they hold more upward rebound pressure movement and last much longer. If these brands of shocks were available in my area, I would have installed them on my Safari. For more details, surf: http://www.bilstein.com/index1.php
- Install / use brakes on attached trailer. For my home's backyard tasks, I pull 2 different utility trailers. A small 4x6 (no brakes) and a 6x10 (with onboard electric brakes). With onboard electric brakes, my van stops "much faster" then my loaded 4x6 smaller utility trailer. To me, the brakes on a Safari/Astro van are only sized for the vehicle. Any trailer above 1,000 lbs (behind a Safari / Astro van) needs its own onboard brakes. One's stopping power with trailer's onboard brakes is dramatically increased. Like comparing night and day.
To answer your immediate question, go with "Timbren SES 2,000 lbs" upgrade in rear and go with Bilstein brand shocks.
Hope these items helps...