I would NOT use a carb in this application. If you want good 4wheeling, reliability, and MPG's then even a TBI unit wins over a carb.
Don't go over 215º on the intake duration as noted and no more than 220º on the exhaust (about a 5º split). A good set of long tube headers helps a lot and in that climate/driving I would DEFINITELY get the stainless ones.
I would expect about 15MPG off the details you're describing.
Really a good low buck combo (low buck for around here) would be a Vortec 350 with a zz4 cam. Clean up the head castings a bit, slap on a set of stainless headers and get it tuned and you'd have a VERY reliable engine with great mid range and mileage.