The 24 is right on the money with anything up to a 125 shot, I ran a 23 with the stock heads and a 150 shot (11.70's)... gapped 'em at .035 of course
Currently, I use NGK R5671A-9 w/ a 200 shot, and have used the Autolite Racing plugs in the past with good results, but have easier access to the NGK's ...either are good IMHO.