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Based upon the picture, it appears (to me) hard to believe that these could maintain proper toe alignment and camber under side loads. Norval has posted how to fabricate a "notch" in stock T-arms and maintain enough material around the notch to maintain the original strength if not adding strength.
First impression is that these would not hold up. I would have to see them personally to render an opinion. Interesting idea, but I would go with an offset arm before I mess with those.
For the price I would just pay extra for an offset arm. It is hard to tell if they used some good quality plate in that modification. If not plate steel I would question how well they would hold.
That being said, I saw several hundrad at the Corvettes at Carlisle for sale used that looked close to new. Dozens of rebuilt units in standard and offset with pricing at less than $400 per side.
Those look like they need just about everything.
It's the rectangular "boxing" that gives the arm its strength. Without that, you'd need some pretty heavy stock welded in there to give it comparable strength and rigidity. I would not trust those.