I have never seen a pickup towed behind a class 8 using the Holland hitch. if I were you, I would fabricate and install a regular hitch and receiver. That would be the safest easiest way to go IMO
The guys who use the clamps you mentioned are guys who deliver trucks all over the country. They tow their pickup or car behind the truck they are delivering. They have to use a clamp hitch since they change trucks every trip.