In my experience, engines with high lift cams that have that lopey idle rarely perform well in a heavy truck,when it needs more low end torque and HP than at high rpms..unless you have low gearing to keep the engine spinning fast enough to stay in its peak power band,you wont be very happy with the way it performs on off road crawling use and slower city traffic driving..it'll foul plugs at low speeds and be herky-jerky in traffic,especially with a manual trans- and fuel mileage will be very low..
Over-camming a 4x4's engine is a common mistake many make...hot cams work best on race tracks ...
GM puts "peanut port" heads with smaller valves,and cams with pretty low lift on most truck big blocks in the 70's to improve towing ability and low end grunt,at the expense of a few HP at higher RPMS...a 454 is not a short stroke engine and wont like being wound out tight a lot...they are better suited to lower rpm and high torque output at the lower revs..
I've had four 454's in bone stock form from mid 70's cars in a few square bodies and one in a '72 Chevelle Wagon that was put on a 4x4 Suburban chassis and despite the fact they were all "smog era" ones that were the low HP versions,I never felt the need for more torque or HP in any of them...all I did to them was try different four barrel carbs and intakes,one needed a new cam (had flat lobes) and I put a Sealed Power "Speed-Pro" cam in it that was ground for towing/off road low rpm uses and that engine really woke up after that was installed..
One 454 I had in a '74 C-10 would get 13-15 mpg on highway trips with a Holley Economaster 450 cfm carb on it...I was told that was "too small" and I'd end up burning valves,but that thing ran great and did not ping,and if anything,performed better than the others I had factory Quadrajets or Carter AFB's on...those all got about 11-12 mpg no matter how you babied it or carried large loads,or empty..
