Looking at the schematic, there are several parts that would be easy to change when doing a cam install. What should be replaced when doing a cam install?

valve seals
valve springs (obviously replace with hd springs for high rpm)
valve retainers (are new stock retainers ok?)
valve keepers
valve lifters
shims
timing chain

anything else?

 

no one? Surely someone knows this stuff.

Can valve seals be replaced from the top without taking the heads off? What about the other parts?

 

I didn't find any seals when I took my heads apart.

You can replace the buckets and shims and that's about it if you are not going to remove your heads. And the chain, of course.