I remember seeing the phrase "98% graphite on a rod when I was a kid (probably around the late 70's)... what does that mean, and how does it compare to other graphite rods of yesterday and today? What's the history? Is it the same as standard/33 million modulus?

That particular marketing phrase was meant to emphasize that the rod was comprised of all graphite fibers; i.e. that it was not a graphite/glass composite. They were at least smart enough to back off a 100% graphite claim, since there was most likely some small amount of glass scrim in the prepeg.

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Gary,
In the 70's no rod was made out of even 50% graphite by either weight or volume and I do not think when you examine the amount of resin in modern blanks by either volume or weight that it is possible to build a blank today that is 98% graphite even if it uses graphite scrim.
33 million is referring to the modulus of elasticity of the carbon fiber. Modulus of elasticity is the stress (applied force) divided by the strain (deformation).
Graphite rods today are dramatically better than those of a generation ago from several different stand points. However, the modulus of elasticity is only one of the variables and 33 million, which is usally called standard modulus, is not really bad. It depends on how the rod will be used. Standard modulus is low relative to intermediat modulus or high modulus but toughness goes down as the modulus goes up. So if you want a light rod that is very responsive and has high sensitivity use a blank with the higher modulus but if you want a rod that is tough use a bl;ank that is made of the standard modulus.
Unfortunately buying a graphite blank is always a bit of a crap shoot because no manufacture, probably for competitive reasons, reveils how much graphite, fiber glass (most scrim), and resin is used in their blanks. I think that a rod builders only choice is to stick with blank manufacturers that you know to be reputable companies.

Emory, Thanks fore the rod blanks tips