This is from ARB website, under applications
http://arb.com.au/media/products/air...tion_chart.pdf
4Runner
Front
2003 on 8" dia. RG, IFS clamshell, 53mm BRNG 33 (1.31") 30 3.91 & UP RD111
2003 on 8" dia. RG, IFS clamshell, 53mm BRNG 33 (1.31") 30 3.73 & DOWN RD121
Rear
1988-10 V6, 4WD, 50mm bearing ID 33 (1.31") 30 All RD132
1988-10 V6, 2WD, 45mm bearing ID 33 (1.31") 30 All RD132
I think the RD23 is the older version of the RD132, the guys who installed lockers prior to 06 have RD23 and after have RD132.
Tell the 4WheelParts guys just look at the ARB Air Locker application guide it clearly says the model needed.