Sway Bar Bushing/Link Question

[65Valiant310]

I see sway bar link bushing kits, but what is the difference between heavy duty and standard? (rockauto for reference)

Are the heavy duty bushings firmer providing less "give" when you push the car?
I have an addco on the front of my 65 and want to replace the stock sway bar links/bushings

thanks in advance