I have a SBC with centerbolt valve covers. No holes on LH side, breather and PCV on pass side. Need to have PCV in drivers side. Been running the tall, plain, polished valve covers for a bunch of years.
Now that you're caught up...
I stressed and shopped, trying to find something that had the style I was looking for, tall enough to clear my 1.6 roller rockers, and having the holes I needed. I finally settled on some Cal Custom ones that I figured would match the finned intake I have. Put the order in to Summit, and wait. They arrive in a couple days and I'm excited. Opening the plain white box, I discover that the casting is not perfect, but fine for what I want. The polishing is also not perfect but good enough for a non-show car (I could deal with that later).
Fast forward to install day...
These covers are designed to use a stud instead of long bolts. I figured it out after trying to find the 1/4-20 bolt hole with the 6" long stud, with no guide tube inside the cover. I put 2 studs in the head, then put the covers on. Actually, I fought the slight splay of the studs until I got them lined up and threaded through those tiny holes in the cover. Guess what??? They only have about 3 threads poking through. I decided I would make my own longer stuffs using 1/4-20 all-thread rod. Yup, that stuff isn't perfectly straight, but after setting up one head, I put the supplied nut and an acorn nut on top just to see how they looked.
After seeing it all on, mocked up, and how it matched, It's all boxed up and on the way back to Summit. I don't blame them, I just wasn't happy overall.
The acorn nuts looked the better of the two, but still not great to me.
I ended up punching a hole in my existing LH one, and re-routed for the PCV. Eventually, I will blast these for a cast finish to somewhat match my intake. I even found some metal baffles in my parts stash and epoxyed them in (after splitting a boss with the screw.) You can also see the guides for the hold-down bolts. These were cheap valve covers I picked up from a Car Craft show vendor years ago. way better fit.