Hmmm, decisions, decisions.
If you have decided on Reese, the dual cam setup is best. They also manufacture a setup similar to the E2, and of course the tradition WDH with a friction sway bar. I would stick with the dual cam for that size trailer being pulled with a mid-sized pickup.
Now on to spring bars. You are gonna have to really concentrate on loading that trailer front heavy to get it to tow good. The listed tongue weight is a little less then 8% of the total listed weight. That needs to be at 10%, and 12 to 15% would be better. With the weight usually put in the kitchen and fridge towards the back, you probably need to really load up under the bed, the front wardrobes, and the front pass-thru to get your tongue weight up.
Now, all that being said, 600 lb. spring bars should work. If you approach the GVWR of 6119 lbs, then 12% of that is gonna be over 700 lbs., the 800 lb. spring bars might be needed, but I think on that trailer you will be lucky just to maintain a 10% tongue weight.
So, IMHO opinion, a Reese round bar setup with 600 lb. bars, and the dual cams would be a good fit.
Chap , DW Joy, and Fur Baby Sango
2006 Ford F150 Super Cab 4x4
2008 Surveyor 263