Do you have manual or power steering?
I just installed Doug’s D453R headers on my 75 Dart Sport. I went with the R version (raw steel) because I assumed dents would be needed. My car was originally a slant six with power steering but just got a 360 small block. I have aluminum Edelbrock Magnum heads, Schumacher conversion mounts, manual brakes, and the original power steering column with manual steering gearbox and an adapter between the steering gearbox and column.
With all these variables, on the left side I had to dent one tube to clear the original steering coupler, and two tubes to clear the left torsion bar. Even with engine mounts removed completely, this engine and header combo could not be positioned anywhere better to clear everything.
With that being said, the quality of the bends and the thick flanges are very good and I would buy these again for this car even after knowing I would need a few dings.