Do you need a harness bar if you have a cage ??

 

No mate the harness will fasten on the rear bar accross the rear struts BOTTOM OF PIC

 

All depends on the design of the cage.
I had a harness bar fabricated in the back of the car which works with my cage.
Some bought cages will have a bar at the right hight some wont
Fabricated ones like Lees, well you spec it so it has a bar built into the design.

 

another pic to show the height as mentioned bt steve