My 66 Cuda

You'll need a counterbalanced flex plate. B&M makes them. 360's are externally balanced and part of the balance weights are on the torque converter. If your torque converter has no welded on square weights on the face, its a neutral balanced converter, in which case you should use the B&M part. Probably some other outfits making them as well. Get one that matches the year engine you have.

Keep in mind that those headers probably wont fit, and for certain will not with power steering.

To change out the center link you need to take loose the tie rod ends, pitman and the idler arm. If you have a pitman arm puller that can be a less destructive way of removing them vs using a "pickle" fork.

In order to swap the steering box you'll need to get a steering coupler that works with the manual str input spline and longer steering shaft, or an adapter for the shaft to the box. Flaming river or maybe mancini makes these parts (I think).

Your choices on exh are spitfire shortie headers, oem cast iron for 66 and older A bodies, or TTI long headers. You'll need a bigger radiator as well, and a disc brake, and rear axle upgrade would be well advised.