It’s 3/16” steel plate for both parts. The pass side plate just covers the bumper holes. I’ve tried to cover/fill every hole where fumes/fire might find its way back into the car.
Thanks @patrickstapler. Been a while since I measured it and for some reason I had 5" or 5.5" center to center in my head.You might want to double check that diameter. The slots on my car are .540”. This is about right for a standard engineering tolerance for 1/2” bolt. The approximate distance center to center of the slots on my car is 4” which would equate to a 3 1/2” inside u-bolt.