For regular street plugs autolite 3923 or champion rc9yc are pretty close at 10.75:1 with a wedge/aftermarket head application. The hotter 3924 or rc12yc also works but is a little on the hot side. I've tried to remember ngk numbers and have given up, LOL. Someone else can help with those. I'm going to start out in the same ballpark on my 572 with a little less compression. I would probably start with the colder 3923 on yours and see how you like it. hope this helps.