The attached picture shows a van chassis (left) and a sedan chassis (right). The van chassis arms are fully closed while the sedan chassis arms are open C shapes, but with a box section (second hole from the top) on them.
The diagram has a circle where I expected the front chassis would join the rear chassis.
If the front part of the chassis is replaced, does that mean the inside closed part of the van chassis, nearly the full length of the arm, has to be picked off and then attached to the new front part?

Pic
TwoChassis.jpeg

Diagram
ChassisJoin.jpeg