Well the 1988 500 & 250 swingarms are the same:
"As copied from BikeBandit Oem parts pages"
33001: ARM-COMP-SWING,SILVER 3734402-001 $434.11
Open up two windows on your monitor,
Go to one of the larger retailers, look up the models you want to compare
in two windows next to one another.
Tuck\o/