Thats a big offset rim. The most I'd like to see is 30mm, but finding RWD offset rims is not the easist thing. Standard AE86 is +26, or atleast my 15x6.5 +26 fit with slight strut rubbing of tyre wall upon tyre deflection.
Anyway, re your question: Any import shop should set you straight. Just say you have S13, don't complicate things by saying AE86. Both S13 and AE86 have 114.3 PCD. Price: unknown. If you were in SA, JMS would be the go, but don't know interstate import shops. 15mm spacers that bolt to the hub would be more legal, but all spacers are illegal, just the good ones are hard to spot!