ET in the 30's is too low for an 8" rim. it will stick out and also look weird on an 8 inch.
Subaru's running 8" are normally ET45 - ET51
Two wheel offset calculators here :
http://www.1010tires.com/wheeloffsetcalculator.asp
This one goes into more detail :
http://www.rimsntires.com/specs.jsp