Autolite AR Racing plugs AR33 thru AR35 depending on heat range needs.
they are shorties to clear headers on both straight plug or angled plug heads, non-projected tip, and really good quality. I have had only one plug failure in over five years, and change them out once a year at beginning of season, just because... and race hard at dirt circle track every weekend thru the summer. You can probably get them from a local parts store, but I order mine through online speed parts outlets. Jim