I don't know if this is exactly what you had in mind. I use the built in Mail program and Palm desktop. I don't use iCal. I don't sync my mail to my Palm either. If I need a copy of an email, I try to dump it into a memo. There is a nice, free program called Note Taker, which can sync larger documents to the Palm. I use Mac Journal as my email archive. Anything I want to keep goes into an email archive journal, by use of the Services function.
I really don't have a lot of programs installed on my Mac. I have Tex-Edit plus, which I don't use that often. I do use iSilo quite a bit, to dump files onto my Palm. The built ins on the Mac are really good programs and suited towards a plain and simple system.
This program creates a virtual "notebook" where you can type in lists, and organize them. You can also import items from other programs (text, e-mail, pictures, documents) via drag & drop, or it's "Clipping" service. This makes it easy to import e-mails or stuff found on the web, into the lists, allowing you to keep your e-mail's in box truly an "in box" and not another place to accumulate "stuff" in.
It has many other neat features that have no bearing on GTD, but if you're interested go to their website and take a look (there's some good online demonstrations there).
I know you only wanted to use the "plain vanilla" programs, but I've found that the $50 spent was well invested.
I use iCal for my category lists. If you make a different empty calendar for each category it works just fine. It does not sync by category to the Palm though, so you have to develop a priority system. I make all my @calls "very important" and so on. This allows for all the calls to be in the same place. It is kind of a pain in the neck, but there are advantages. You can make new todos in a category by just dbl clicking instead of using the drop down in Palm desktop. You can make a "memos" "calendar" and make each one the title and use the notes section for the contain. It syncs just fine. We really need a good mac app for GTD.