I agree you dont want that big a tube header on your combo. I used 1-3/4 on my old mild 440 combo and it dipped in the 11.40's with a full exh when it was in my 63. You can get Hedman 1-3/4 for a good price as thats all you need for your combo as like everyone says the large tubes will hurt the low end torque alot. Ron