that engine was throttle body injected TBI so the fuel pump was in the tank.
HP for a 5.7 in that year was about 210 hp (some for that year were 190hp) but the 4x4 i think is 210
mpg for a 4x4 with 31's and a high rear ratio of 3.08 will probably be around 11 (thanks to the tall rear ratio and big tires) or so in the city and maybe 15-16 on highway---just a guess. I wouldn't go higher than a 31 wheel with that ratio. I have 33's on a 3.73 4x4 and even that seems kinda tall for my taste.
that's a good year for 5.7. Very dependable and durable and in my experience, the piston rings and valve seals will last if taken care of. My '91 has 208,000 and the only time i put oil in it is during oil changes. www.delbridge.net/suburban