Rear Spring

[Big Fish]

I purchased what I thought was a 340 pound "TRW" spring, turns out when the carton was opened there was a 315 pound spring inside, even though the carton was clearly labled with the 340 pound version. Does anybody have some thoughts on this spring? I need to either return the 315 pound spring for exchange or install it. I am anticipating running about 350 hp with a 350 and 3:55 gear :J