Originally it had AC R43S plugs. You could bump up to a slightly hotter plug like original in the R44S. There's AC's Rapidfire #7, among others that are pricey. I haven't heard anybody say that they are worth the cost. NGK has XR4's. Autolite has the #85's. There's your major choices. I left Champions out because with my experience I have found that they do not survive after they have been flooded just once. If you decide to install a higher output ignition, like an HEI, then your choices are a little different. My recommendation for your original 350 would be the AC R44S.