Nice to see that my quest has inspired you (as you already mentioned in my topic). Now for suggestions; think about the limitations that they had then and try to limit yourself in the same way. Some very good suggestions in that direction are already mentioned here.
For drums you might search the web for some studio recordings of prog drummers. I have some studio-takes of Bonham smashing away and I'm sure there is more to find. Get the Bonham tracks here:
http://www.saladrecords.com/bonhamfiles.htm
I also suggest you grab the Elektrostudio VSTi-pack, link is in my topic. Gives you instantly all the keyboard sounds of that time