SR 104 shouldn't be to hard to beat. Let's say the spellcaster in question is only level 84 because he made some Epic spells or something (needs a 20). Any caster not focused exclusively on buffing should have Epic Spell Penetration for +6 (needs a 14). FR stuff is used, so a wizard could have all kinds of stuff and a cleric would have 5 levels of Heirophant - so the Harming cleric could have +10 or +8 spellpower. That's a 6 needed to beat the SR. The Pale Green Ioun adds to caster level checks. The apparent cost for an upgraded version is 10000 x bonus^2. A +5 no space version would be very cheap. An Epic version would have an even greater effect, but would actually cost an appreciable amount. So defeating 104 SR is almost automatic. We could have Candles of Invocation, Karma beads, etc. Wizards could have Archmage, Red Wizard, Shadow Adept, Elemental Savant and so forth so even better spell power.
The reason I used an Epic Dispel was so that you also have the opportunity to counterspell. Rip away the dragon's buffs with Disjunction or Hyper-Dispel, shut him down with counterspells so his own spell ability is useless, and kill him. That way, even if your 1 round kill attempts fail, he stays locked down so you can beat him up slowly.
Another attack method might use Soul Strike from R&R, since it deals Con damage even on a successful save. Fire off a bunch with Automatic Quicken Spell and Multispell, and watch the Con damage rack up.
Using the BoEMs makes it easier. The dragon will still be shut down because it's easy to win caster level checks against him, and you can fire Squamos Pulse that will deal lots of damage and strip his natural armor.