The tapered seat plugs will run WAAAAYYY too hot because they can't transfer heat to the head properly. They'll fail within just a few miles and give the engine an intermittent miss that's hard to isolate. R45 plugs gapped to about .040" ought to work very well with the HEI. CR45 commercial plugs will work even better, but they're almost impossible to find now.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!