Look for a set of 81 heavy 3/4 or 1-ton heads, they had bigger intake valves and slightly better ports. Then, find a cam from an 82 or later heavy 3/4 or 1-ton as they stretched out the intake duration to make up for the heads having smaller intake valves... Between that, a little fuel bump, disabling the EGR, a timing bump, and a free flowing exhaust (big block headers fit with some modification BTW) and our 82 service truck has some pretty decent pep... About 170hp, can't really complain too much, but it is quite a bit more responsive as well and has no issues at all lighting the tires up (33x12.5's)