Best thing to do is measure your track width with your standard setup. Then measure it with the ATS and try and match it up. Everything will be a little different in the rear end because you're taking the angle out of the arms. With a 3 block I would aim for a 2 block forward and rearward back there.
As far as finding a R102043 in stock anywhere....good luck. No one used the ATS system before Reedy therefore they weren't stocked much at all. Now there's this huge surge for these parts that are mostly sitting in Taiwan. Gonna take a little while to get them stateside. Watch
here as they will have them first.