You want the end links as vertical as possible at normal ride height. So loosely assemble the bracket, links and bar; then set the car on it's wheels while you mark the bumper brackets for the bat attachments. You may need to tweak the bar arms a bit wider or narrower to get them to line up. Addco's advice was to stick one end under a wheel and pull/push on the other end, to bend it a little. (My rear bar was off by several inches, apparently because they supply the same bar for TR3 and TR4. Had to get different brackets from them, too.)
Don't recall now if that's what the instructions said, but I installed the flat plates between the bushings and the bumper brackets; with just a nut & lockwasher inside the bracket. Held up great for some 20 years.