A couple of those stud holes are deep and wet and will need sealer on them.
The 1/2 in depth is dry and proper for the others. Originally the studs have a slightly oversize thread on about 5/8 in of the end that threads into the head, to lock and seal them.
I hunted all over for new studs(because the originals are almost allways shot for me). I could not find "studs" of that length, even through commercial bolt suppliers or industrial suppliers.
I ressorted to buying grade #5 3/8 bolts about an inch too long, hacksawed the heads off, and threaded the short end to go in the head. With adjustable dies you can even make the 'interference' threads to fit snugly in the head. IF you're a perfectionist you could use stainless steel bolts.
I find I have better service and luck with the small additional cost of using s/s nuts and washers, rather than brass. I've had problems with the brass nuts shrinking from the heat cycles and getting tighter than the hubs of h---. They didn't rust, but got about as tight.
And ofcorse, use 'Neversieze' type lube on the nuts.
I allways assume that I will have to work on everything again some time, so I try to make it easy for myself later. No short cuts or cheats that will bite me later.