I have a problem with my Holley 600 (4160)
These work amazingly well and they aren't that thick. Also you might consider pulling that intake and blocking those heat cross overs too.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL-9265&N=700+115&autoview=sku
or if you want a center divider type:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL-9266&N=700+115&autoview=sku
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