I use the stock arms with HR Parts boxing kit with my ATR bar.
Works just fine with their bushing kit that's greaseable poly. also.
The HR Parts lower arms brand new with greaseable bushings should also work with that bar I believe, I use the HR Parts bar with my other car that has those lowers however.
If you have or know a welder you can box the stockers up rather easily. 1LE bushings are also said to be good to use.
Make sure you weld the inner reinforcements inside before boxing up the arms to make them stronger.