I don't know about the 1-7/8 tube size but I just did the 1-5/8 to 1-3/4 standard port headers from to in the wife's '67 Cuda.
I did have a small figment issue with the #1 tube hitting the manual steering box on the top inside bolt. Shims helped but in the end, I ground down the bolts head. There is minor interference now.
Otherwise, it was EZ.
Do note that the header flanges bolt holes were very tight in fitment.
