My MK IV's do. The holes are about 0.020" off and need to be opened a little. I've never done it, I'm just assuming you can. Others chime in and let me know if I'm wrong.
Apparently they are there and were used with gear drives.
Installing Roller Camshaft in Mark IV Big Block - What Mods are Required? - Chevelle Tech

See edit above. Found on Chevelle forum
23900-gen-6-cam-mark-iv-block.html

I used the stock timing cover on my Gen V 525SC with a cam button when I retrofitted a roller cam.
I used a button with the built in bearing. Never had any issues.

I did opt for a roller button.
​​​​​Many have run the nylon without issue.
Will have parts this week and make a decision.
My biggest concern with this would be timing issues. One post I read guy had 14° variation in ignition timing due to cam movement.

You probably know this, shim the roller button so you only have .003 to .005 end play.

That much movement could be a combination of to much distributor end play, chain slop and cam end play.