Bigger isn't always better. Depending on whether it's 500 or 600, you could go either way. I was going to go with 1 7/8 TTi on my 408 stroker which is 500hp. I spoke to the TTi people and they told me that 1 5/8 was just fine for my horsepower and the 1 7/8 would be more than I need and would rob me of torque. He said if I was in the 600hp range I would be better served by 1 7/8. Just thought I would pass along what the header gods told me.