Hi Dig,
Welcome to the world of "fine print" and trying to sort out a WD hitch. It can be a maz of numbers... but we can help you sort through this and most of all, learn what all this means.
The Reese trunnion bar hitch has tapered rectangular WD bars. The Equal-I-zer hitch has solid square trunnion bars. The Reese flexes differently then the Equal-i-zer and that chart will not apply very well.
To make a good working hitch sizing match up, things that need to align to make all the fine print work out OK.
1. The truck receiver, what is the rating in weight disturbing mode? Can it handle a 1,200# rated WD hitch?
2. The WD hitch needs to be rated heavy enough for the trailer loaded tongue weight. If you have a lot of weight in the truck bed behind the rear axle that is loaded "after" you adjust the WD hitch this needs to be looked at too. In this case you have lots of WD bar capacity with the 1,200# WD bar.
3. The trailer A frame and the trailer frame header needs to be strong enough to not bend when subjected to the high loads of a WD hitch. In this case, Sunline did not build your A frame and frame header strong enough to handle the forces of a 1,200# WD bar. While you have a 2003 camper, Sunline did a redesign in 2005 on some of the trailers that made the A frame like your 2003. They found out the hard way if the trailer has a real heavy tongue weight, 1,000# and up, it could and did bend the header and twisted the A frame. We have a real long post on this. It rears its head badly on the 2005 - 2007 T-2499's. Using a 1,200# WD bar on that light of a frame header is not a good idea.
We do not know what your truck receiver rating is or even what your truck is, but I can only caution you that number 3 above is a reality. Item 1 can be a problem too if you are using a 1,200# WD bar on a truck receiver only rated to handle a 900# WD hitch or anything less then the 1,200# bar.
Aside from the sizing top 3 needs above, trying to adjust a 600# loaded TW camper to a 1,200# WD bar is not easy on a light duty truck. Meaning not a 3/4 or 1 ton truck. The WD bar adjustment is so far away from the good working zone that one small tweak in adjustment and you either have too much WD or none at all. The truck will ride badly going in and out of having WD adjusted corrected when you go over bumps as the bars are not flexing very well. If you have a 3/4 ton or 1 ton truck you can sort of get away with more as the truck can almost handle 600# with no WD so going out of WD adjustment does not really affect you so much.
Point being, you will not be happy long term trying to apply a 1,200# WD hitch on a 600# loaded TW travel trailer sooner or later. That Reese chart does not take into account all the factors in your setup.
Here are a few options in the Reese brand.
800# Reese SC hitch. Has intergrated anti sway with the hitch. Need to add tow ball too this and check that the standard WD shank will work with your truck. If not, we need to deal with the shank
https://www.etrailer.com/Weight-Dist...e/RP66153.html
If that cost is too much, consider this hitch and add a friction sway bar.
https://www.etrailer.com/Weight-Dist...e/RP66021.html
Here is the sway bar
https://www.etrailer.com/Weight-Dist...ies/83660.html
And a tow ball.
https://www.etrailer.com/Hitch-Ball/...ite/19286.html
This thread may help too. The hitch shank length needs to be checked before buying anything above. If your truck requires a high drop shank to level the camper out, the above hitch sets may not work right and you have to buy another shank.
http://www.sunlineclub.com/forums/f7...tml#post137593
There are other brands that will fit and work too. We can run through them if you find a brand you like.
Hope this helps and glad to explain more as needed.
John