Never done it, but I would guess that:
1. Ranger gets weapons specialisation
2. Ranger starts with 2 bonus points in dual wield
3. Ranger gets more HP
4. Ranger gets lower THAC0
5. Ranger gets stealth ability
Therefore a ranger dualled to cleric gets these bonuses of rangers as a starter. I would dual either straight at the beginning of the game (having put weapons points into mace, warhammer, sling etc.) or at level 9.
Then you have yourself a weapons specialised dual wielding cleric with stealth.
Cool.
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Time is an illusion. Lunchtime doubly so.
Epona of The Laughing Hyenas