I'm not an expert in these matters by any means, but don't people typically install an overdrive alternator pulley when installing an underdrive crank pulley? You might want to check that out if you are switching back to OEM.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |