I used a BPE kick down cable kit that is basically an off the shelf Mopar cable with all the fix’ens that bolts right up to a 904 or 727, and BPE universal cable mounting bracket. My car is a 67 so it came with cable operated accelerator. You can use most any cable operated accelerator pedal from ‘67 on up including any K Car derivative, Aspen, truck etc., until cable-less drive by wire accelerators that came in mid-2000’s, and adapt a shorter cable to it.
I had to shim factory bracket of accelerator pedal out from floor (this may be due to a non-factory replacement floor pan) to achieve full throttle opening on the 390, and use the Chrysler throttle shaft adapter to get transmission cable and accelerator cable to play nice with each other. It all installs in an hour or less, and can be dialed in quickly once installed. You will need one slightly longer carburetor mounting stud where cable adapter bolts to carburetor flange.
Yes, that is an o2 sensor to aid in carburetor tuning just below collector. My engine has a big cam with a lot of overlap that makes for very low idle vacuum, something a Holley 390 does not like, and this contraption helped a lot in sorting out jetting.