[Cabnchassis]

Every 454 from these trucks I've spent time in only has one mpg rating and its been 10. I think my 350 is a dog on fuel and gets 9-10mpg city but it will still get 14-15 on the hwy with mud terrains and 4.10s in a k2500. I pull a 10K trailer to shows for a friend of mine with mine and it really isn't that bad even on long grades. My truck has lived under a trailer most of it's life cause the PO had a gooseneck and 5th wheel. I have overdrive to go with my 4.10s too so that does play into the driveability a bit but still a 5 mpg loss is nothing to sneeze at. Not to mention these tbi 350s really last. I've seen several still in good shape with close to or beyond 300k and i'm sitting real pretty at 210K.

Having worked out of both trucks I wouldn't personally do it, but I get irritated at trucks that have little power and use loads of fuel. I used to drive a 94 CC dually with the 454 and as a work truck, it was miserable on fuel and not really that powerful an engine. My 92 came rated 210/300 HP/tq the 454 was only 230 hp and 385 tq those same years and was never far beyond of that in TBI configuration. Your truck would have been like 185/295 so you'd gain 55 and 90 respectively but those ratings don't mean much 20 years later they all age a little different. I especially wouldn't pull out a used tbi 454 to replace a reliable TBI 350. I've seen a lot of high mileage tbi 350s over the years. Don't take my .02 though cause the 454 does sound a lot better and that right there might be worth the whole thing if you like hearing the pipes ring.