Help identifying sway bar
Ok question #2
If it's for a pre 73, will it work after I install the 73+ bbp swap?
Yes sir. The early sway bar is a long limber timber that goes around the front of the K. 73 and up is a shorter bar routed through the middle of the K. It had shorter end links to, attached at a different point on the lower arm. The forward mounted disc brake calipers didn't collide with it.
The typical solution always was to switch the disc brake spindles left and right so the caliper mounts rearward. There is no change is suspension geometry, just longer (f-body) fluid hoses req'd. In recent years some have discovered they could place the spindles/calipers forward like OEM and use very short end link kits loaded below the attach clip instead of above. A bit of ground clearance lost in that. End link aint much, very easily bent.
Since your aftermarket bar has already deleted those low hanging triangular forward mounts, and its end links will likely attach to a clip added at shock bolts, I would recommend the old standard, disc spindle L to R swap.
F-body hoses, make sure the bleeders are at top of caliper, happy moparing.