Reese makes at least 4 different prices levels of weight-distributing hitch. Don't even think about the cheap Pro Series. The SC is better, similar in design to an Equal-I-Zer brand WD hitch, but not good enough for me. I insist on at least a Reese Strait-Line hitch. The Strait-line (and the SC) has bed rails on top of the floor of the bed. If you want a clean empty bed when the 5er hitch is not installed, then you want the top-of-the-line Reese Elite hitch, which has under-bed rails.
The Strait-Line hitch is available as either a round-bar design or a trunnion bar design. The round bar design reduces the clearance between the ground and the bottom of the installed round bars, so it's easy to drag the bottom of the hitch on the ground. The trunnion bar hitch has more ground clearance. So order the one with trunnion bars.
Also, the Strait-Line hitch is available with and without the shank. You want the one with the matching shank.
The Strait-Line uses the Reese dual-cam sway control design, which works a bit better than the friction design used by the SC.
And it's available with 600, 800, 1200 and 1500 pound trunnion bars, so order the one that will have more tongue weight capacity than you will ever need. Assume tongue weight of 15% of the GVWR of your heaviest trailer, and order the weight capacity for more than that number. You can adjust the amount of lift a hitch with a high weight capacity has by the number of chain lengths you use when hooking up. But if you have an 800-pound hitch with a 1000 pound tongue load, there is no adjustment you can make to have the hitch handle the higher load. So pay attention to which weight capacity you order.
Arch gave you the part number for the one with the shank and with trunnion bars rated for 1,200 pounds max tongue weight, 66084. That's probably the most popular one for smaller and medium-sized TTs with GVWR up to around 8,000 pounds. Here's a good source:
Strait-Line Weight Distribution System w Sway Control - Trunnion Bar - 1,200 lbs TW RP66084