which spark plugs do i use?

hi there folks. i wish to replace the sparkplugs im using for new ones - they have been in the car for 5 years i know of and have done probably around 3500 miles. They are a little corroded around the top and would clean up ok but i think it's time for some new ones.They are Autolite AP45.
Autolite plugs are not available in New Zealand, so does anybody have any recomendations for any other brand plugs i could follow please? Its a Paxton supercharged car running dual 2 1/2 inch pipes thru flowmasters. Also what gap do you think i should have in them......thanks Graeme.