This is my first post, other than the intro.
As to David and Vicki's original question: It looks to me like there is only one shock for the 3500 lb. axle on the 2499. So unless you flipped the axle, Monroe will know what length. The 2499 has an I-frame which isn't one of Monroe's options or is the I-frame the same as "C-channel frame with channel out"?
I am also looking at several ways of improving the ride, but in my case I'm not sure it's the trailer's problem. Stuff in the trailer, including a stove top cutting board, doesn't really get tossed around. I think even GMC's HD shocks are not up to the 2499's TW. I'll add more of my experiences if this thread continues.
I have no affiliation with this company and haven't even bought anything from them, but they have a good website.
The shocks are here http://www.cerka.ca/catalog/32SHOCK.asp
and if you click on the part no. you'll get an exploded photo.
I'm not suggesting you buy from this company because of cross border hassles and more expensive CDN$ and shipping, but I think a trailer parts company like this should be on the outskirts of a nearby metro area where you live. And unless you've got a good RV dealer companies like this likely have more expertise and better prices. Perhaps other readers can point you to a similar source where you live.
The Dexter equalizers are here http://www.dexteraxle.com/e_z_flex_equalizers
There are two kits, but for the extra money you get bronze bushings and greaseable bolts which would be worth it for a high mileage trailer or towing long distances.
If money is no object, try a couple of these http://www.trailair.com/products/centerpoint/
. At least you won't need shocks then.