The stamped steel covers that are everywhere are junk. They often leak badly. In my observations the stampings lack embossing around the bolt holes, you can easily crush and distort the covers and still not seal very well.

So, I got one of those inexpensive cast aluminum covers off ebay. They actually look like they'll work quite good after you clean up the flashing, chamfer the holes, and run a flat file over the flange. One problem, if you need a vertical timing pointer, like stock, there isn't anything that really works well. none of the stamped tabs will fit with the thickness of the casting. The older SBC & 'aftermarket' pointer location is 10degrees advanced from the keyway and those are the pointers & damper marks you'll see everywhere. However the later SBC rotated the marks another 30 degrees to where they are almost vertical.

To use that cast cover and have a robust timing tab, I cut down one of the cheap chrome tabs & affixed it to the cast cover. I used aircraft aluminum rivets, verified clearance to the cam bolts, and used sealant upon assembly before riveting. Turned out pretty good.