Sorry, I'm sure this has been discussed alot. I see people have varying answers. I'm going to be running .120 DOM. Are the 6"x6" plates acceptable or do they need to be tied into the subframe? Is 1-5/8" tubing adequate for all tubes? Can the lower main hoop diagonal bars be tied to the tunnel? Or do those bars have to go to the "subframe"

 

Since you are requesting about 8.50, this must be for a full cage and not just a roll bar.

Minimum requirement will be 8 point. Main hoop(2), Diagonals from under cross bar down to driveshaft tunnel or subframe(2), Rear tubes(2), A-pillar bars with halo bar around roof and at least a drivers side door bar however it's recommended to also install a passenger door bar. Every other tube added is there for a reason but is not required for an 8.50 cert. Since third gens are a unibody, 6x6 plates at every point that a tube attaches to the floor. The plates should be welded to the floor and can be bent or contoured to fit the floor where you intend to mount a tube. Although it will pass, I do not recommend bolting the plates to the floor and the floor structure in a third gen does not allow proper shape or access to have a plate above or below the floor sheetmetal.

0.120" DOM is the required tubing. 1-5/8" is required for all the above mentioned tubes except the diagonals. Extra tubes such as knee bar, sill bar, door bar, rear X bracing etc have minimum requirements depending mainly on the length of the tubes.

This is how I installed my cage but I added a lot more bars. Like I said, they're all there for a reason. Has no problems getting an 8.50 cert.

https://www.thirdgen.org/forums/fabr...roll-cage.html

 

My cage certed 8.50. As you can see the diagonal bars go to the tunnel on a plate. The X in the door bars was simply cosmetic per my request. They arent a requirement in an 8.50 cert cage.