BBC plug gaps

looking for opinions on the gap for my 454 fresh built 30 over full roller valve train timed at 16 initial 35 total stock valves rpm air gap 750 mech holley big tube headers and 3500 stall t350 with 3.73 out back. I'm running the same number plug in it as what came when I bought the Elky in 2005, machine shop said to gap it at 30 however same shop told me that number last year on a small block we built. Then we got to the dyno pro he quickly changed it to 40 played with the advance and picked up 100HP, embarassing but great. Hate to go back to him with a BBC as far out of wack as last spring SBC. In addition to the gap, I have buddies who swear by platinum plugs, but how do I know which is the best number to use?

I'm using Autolite AP25's gapped at .045.

That's a platinum plug and they hold up great!:D