I have the TTI 2 1/4" primary 4" collector headers on my 572" hemi in my '70 cuda. The front end is all stock stuff, except for the motorplate. Had to cut part of the original motor mount bracket off the K frame on the driver's side only. Manual steering and manual brakes.
I only had to clearance one tube on the passenger's side to clear the torsion bar. Other than that, they fit great!

Depending on how your motor is built, the 2 1/8" headers will likely be plenty big. They will probably make for a better street/strip header since they will make more lowend torque, especially if your hemi is fairly mild. Not to mention fitting better.
I went w/ the big ones b/c I wanted every last bit of power I could get (over 800 on just the motor, then there's the nitrous) and I can put up w/ a lot on the street.