I've put Use Autolite 104's gapped to 0.060" on a 3.4" GenV setup running more boost than yours (more restricted exhaust) and had no knock or "spark blowout" issues. Anyone telling you to gap smaller probably hasn't actually experienced spark blowout and is just parroting something they heard. As for the plugs - ALWAYS start with the hottest plug you can, scan for knock, then go a single step colder as needed. The most common spark plug used in 3.4" pulley setups is only two heat ranges colder than stock; the AL104.
