I'm unsure on the stock head, as I've not done any measurements. On the head I have on Vixen, I had to use a relatively low lift (.465) in order to utilize some new valve springs I already had. I made no modifications to the stock guides nor did I use any offset retainers or valve locks. I think they have a pretty generous amount of room. Now on my closed chamber head, since I put 318 valves in it, it ended up having enough room for a .750 roller. lol I also cut the guides down and reduced their diameter as well and opened up the spring pockets to accept the Comp 911 1.550 OD big block Chrysler valve springs. It's funny too, the closed chamber head did not quite have large enough diameter spring pockets for those springs, but all my other 5 or 6 slant 6 heads did. You can mock it up with no valve springs and just the retainers and valve locks installed then measure how much distance you have before the retainer contacts the guides. That's what I'd do. That way, you can know about what the max lift it can take. The Comp 901 small block spring will probably work with just about any cam you might put in it.
