i just got a gsr built and sleeve with benson sleeves looks great! i was putting parts on and noticed that the rubber that goes around the crank pulley is dry rotted/cracked... (its a gsr engine) will this cause any issues? i just want to make sure if not i can save $200 thats what new oem one cost! thanks for any help...i plan to turbo this car hoping to run 400hp

 

You can use any b-series crank pulley from what i understand. Not to mention you can utilize a single belt ctr crank pulley for $75.

 

Depending on how badly rotted it is, it very well could be fine. Able to post some detailed photos of the pulley in question?

Yes, Adam_b16a is right, you can use any B-series crank pulley on any B-series engine. Just don't try to use an ODB0 B16 crank pulley if you are keeping all your power steering, it runs a V-belt for the power steering pump.
And yes, you can pick up a Honda factory CTR N1 single belt light weight crank pulley for about $75. It is an under drive pulley as well, I'll have to double check which belt fits it though. I believe it's a 4pk290 Duralast about $7 from AutoZone if I remember correctly.