AWD is definitely worth it if your going to run off road loaded or empty. If your going to build it and put it on a shelf or run it on pavement only on dry sunny days don't bother it's not worth the cost and build time.
Another less expensive but very strong option is using an Axial SCX10 transmission as your transfer case, you can pick them up on eBay for around $40.00. That gives you a 3:1 reduction. Connect it to the 3 speed as shown below. The stock silver can works fine and I wouldn't go any deeper than a 55 turn motor. I've hauled some pretty heavy loads on this with a heaping dump box and it runs through sandy soil with ease.
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Note the GRU in this photo was removed and I've never ran it in this or any other truck.
This is one fun truck to drive!