Some advise would help. Putting new plugs in a early 70's 454. Pulled some of the old ones out and they looked a little rich I think it may be the gas I'm using which was 87, gonna try 91 and put new plugs in. ACDelco R45TS was what was in it, but I think it's because of the headers kind of in the way. I ordered plugs and noticed they had much more threads then the ACDelco, so I'm wondering what the best plugs are, that would work. Can put what was in it, but would like the best hottest plug. Thanks