Welcome to the forum. A couple of things jumped out at me, having done my share of off-road playing with the Jeep over the years. First you mention mild steel tubing - you want to use 1020 DOM tubing for strength, not seam welded tube. I'd use minimum 0.156" wall DOM for the main chassis waist band tube and rocker tubes, and minimum 0.120" wall DOM for everything else. You're putting your life on the line with your chassis & roll cage, so do it right.

Second, you mention "...rock climbs" but then you say "(crashing into rocks and trees)" is your intended use. Are you building an extreme trail buggy, meant to tear through anything at max power for the fastest time, or a rock crawler? There is a distinct difference, especially in the use of the machine. Rock crawling is finesse driving, doing established trails with minimal impact to the environment, while the extreme trail buggies have no concern for leaving the trail as it was when they arrived - they're there to "conquer the hill".

Ryan has given you some good comments, and some added questions about your direction on drive train. Most of the dedicated guys have gone to EFI over carbs, due to the difficulties of maintaining a consistent float bowl fill at extreme angles, but there are carbs that work better for off-road than others if you insist on going that direction. Bottom line, have you looked at Pirate4x4 - link Pirate4x4.Com - The largest off roading website in the world. Those guys are into everything from lightly modified OEM's to the most extreme all-wheel steer buggies and power you'd not believe. Just be prepared for the flaming if you go in asking rookie questions and acting like you know it all.... Just about every question has been asked before, and their search engine actually works.