I bought some thin copper sheets and made mine. But I always
set mine around .040 to .060 preload. I would put it together and run it like it is. If you want to shim the
rockers, go for it. I have run them for years with no problems. But i never had more then about .015 to .020 shim.
Just make sure if you make them the ones that go on the oiling hole has a larger hole in it then the bolt so you don't block off the oil going to the rockers.