Headers for a big block a body?

I bought the complete TTI system, headers to tips, for my 68 383 4 spd Formula S & they dinged a couple of the tubes to clear plugs, etc. I was amazed they'd to that, but they're nice pieces anyway. Only problem is they're 1 3/4" tubes & I've built a 451 stroker & need larger tubes.
I'd consider selling the headers (brand new, in the boxex). They're thermal barrier and ceramic coated.