I know a bit.
You going new or used? Wranglers don't get below $5k for anything worth buying, but Cherokees do. You can modify anything. Quadratec.com is a good place for parts.
The Wrangler Rubicon Unlimited (4door) is a hard core crawler from the factory. It's also big $$.
The Cherokee is light, and very very good in dirt and snow. They stopped making them in 01, but you still see them around. Or you could get a Grand Cherokee very reasonably if you don't mind a few miles.