Front sway bar fit

I don't know about the Dorman bars strength. The original "around the 'K' bar was a long limber timber. Any is better than nothing though. Larger correct bar would be my choice. A larger issue may exist with that aftermarket bar. Majority of aftermarket bars attach at lower shock bolts. You might need to switch sides with the spindles to reposition the calipers and buy new longer fluid hoses.
Correct bar for your 73 front suspension was available in a for sale listing just days ago.