The old AD&D "Deities and Demigods" listed Vishnu as being the following:
Cleric 15
Paladin 17
Magic-User 25
Illusionist 18
Under the 3rd Edition of D&D, a direct translation of this entity would have 15+17+25+18=75 hit dice. For example, Jubilex (a Demon Lord who is a loathsome mass of revolting liquid) is 33 hit dice (d8s). So, a major deity of the Indian pantheon might well have 75 hit dice himself. At the old version's Constitution score of 24, that would mean Vishnu now has 75d8+525 hit points, or 862 on average. His armor class is probably in the 40s, his damage reduction is probably at least 40/magic, and his spell resistance is probably in the 30s. PIECE OF CAKE! Take him down! Fucking dothead!