...very very close to it...everyone having a fit over using a 5/16 socket should shut up, 5/16 = 7.9375mm...so if it fits, it's actually LESS likely to round a bolt off, and if you're yelling at him about it, you're just ridiculous...yes a lot of the fasteners on these cars are metric...but quite a few of them, specifically ON THE ENGINE are indeed not metric...I haven't measured the threads on the fuel rail bolts, so I honestly don't know, but a b-body has just as many metric bolts as it has non metric...now my LS1 Camaro on the other hand...that car and engine are mostly metric.
My friend Dave and I were working on my car (rear lower control arms) one day a few years back, and when we finished we picked up all the tools, and lost one wrench...couldn't find it for the life of us (in the dark). Anyways, the whole winter went by, drove the car through snowstorms and everything, and when springtime came out, I went under the car to work on something else and noticed this shiny wrench still stuck to the nut on the lower control arm...it had bound against the axle tube when we were tightening the bolt, and we'd forgotten to get it off of there, and then when it got dark out that day a whole winter earlier, we forgot...so he got his wrench back.