I am confusing a four link with a four bar. Sorry about that. I should know better than to post by now...
From the AME website:
4-Bar vs. 4-Link: A Tech Overview...
In a nutshell, a 4-link setup is best
suited to Drag Race or Pro Street type
vehicles where high horsepower engines
and large tires are being used. The 4-link
can be adjusted easily to compensate for
track conditions and control the amount of
“hit” the tire takes on the launch. And due
to the high kick-up of the frame rails,
modifications to the trunk and rear floor
are required—often times the rear seat
must be removed.
The 4-bar has longer, parallel bars and
a lower frame kick-up. It is ideally suited
to street and air spring suspension setups,
provides more latitude in setting ride
height and its polyurethane-bushed rod
ends make for a smoother, quieter ride. In
most installations the rear seat can be
retained, with little or no modifications the
seat itself. It’s neat for the street!