DOES THE HDK SUSPENSION K-MEMBER HANDLE BETTER THAN A T-BAR SUSPENSION?

A lot of back and forth here counting angels on the head of a pin it seems.
OP shared some useful info, it works for him, take it or leave it.
Only one maybe minor detail stood out to me nobody has yet mentioned, the not square tire set-up, which effects everything else.
Good handling set-ups usually get close to square.

That being said, the OEM K member is a very robust stout item. With TB's It ties the entire front end together and support and controls the heaviest item in the car, transits all torque reactions the gas pedal generates., and is very much inline in transmitting all front end sprung loads, cornering, steering and braking forces. Lighter weight tubing aftermarket k frames can never match that stiffness, are they acceptable, maybe, but stiffer no way no how, i don't care what material or welding process they use. Is a steering rack better design than a OEM PS box, always. Are better suspension kinematics favored, not matter what the suspension , Yes. The OP seems to have them, Can OEM numbers be improved, maybe, how and at what cost/effort is for the owner to decide. The OP has chosen his path.
I personally have upgraded OEM TB setups, a modified RMS MII set-up, I flew out to Morrison last May to check out their very impressive IFS rack/C6 set-up, but they would not share their numbers after purchase, even with a NDA, so that got put on hold. In the meantime, I'm toying with the C6 MII spindle upgrade option with 2" taller BJ's. since I find the MII spindle and Wilwood Alum hub woefully inadequate on a B Body RB track car with big brakes heat soaking the hubs.