Your booster is not the same as the one on my 70 Cuda, nor is the plate the same as the one on my booster. I converted to manual brakes when I put the 392 hemi in the car because the left valve cover was almost against the booster. The plate on my booster is firmly attached to the booster, I tried to pry it loose so I could use it with the manual setup but it wouldn't come loose. I didn't want to damage anything in case I wanted to go back to power brakes at some point in time (which I did when I put the 5.7 hemi in) so I didn't even bother to check if it was spot welded or just swagged at the base of the mounting studs. It's back on the car now so I can't tell without taking it off. I can say though that it wasn't just stuck on from rust or just being on the car for 30 some odd years.