When I was looking at them last summer, I think the best pricing I found online was at racerpartswarehouse.com. The 6 Series 34 row core was right around $350. I've seen them on eBay for closer to $300, but sometimes the size of the fittings seems deliberately unclear.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |