I see that part is listed as "obsolete" as so many OB parts are these days. However, if you know how that starter relay is actually wired into the system, I am certain there are others starter relays that can work in its place. They may mount differently or even in some other area of the engine area, but function the same way to accomplish the job. Starter relays are merely high current relay devices. And it takes a little amount of voltage and current to allow a huge amount of current to be applied to the starter. So if you can't find one, use another type wired correctly. But make absolutely sure you know how the old relay was wire and make sure you wire the replacement type the same. Similar layout relays don't always have the same terminals used the in same ways. JMHO!
