I'll admit I'm a big block guy, but I was under the impression that only the BBC had oval or rectangle ports and that all SBC ports were the same. I easily could be corrected however. Drag race guys run open headers all the time w/ no problems I've heard of, although they are usually long tubes. I've run my mid-length headers open and had it WFO w/ no problems either. my guess would be that you should be fine.
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