im here to tell you from experience, the poly can show SOME improvement from a 4bbl. but in my experience, the little gain wasnt worth the money. i have run them with the 2bbl stromberg, 2bbl carter, 4bbl edelbrock in both 500 and 650. the 2bbl carter was the most reliable and the strongest one that was other wise bone stock. now my crew with a mild rv cam and a 500 eddy carb ran real nice. if your gonna do a rebuild, get with norm, pick a nice cam and run the 4bbl off the stock 4bbl intake. the wieand is a single plane design and works a lot better at the higher rpm, wont give you the low end grunt the stocker will. i read an article once that showed how to modify the stock intake to open it up and make it perform better, those mods with a nice cam, a 2.25" dual exhaust system, and a good ignition will make the old poly wake up big time.

i have a hard time accepting 60hp gain with just a carb swap, that has not been my experience. but the mileage reported is easy to believe. my d200 crew cab long bed would pull 17 on the open road, so 20 on a better geared truck that may be a shade lighter is totally doable. but as mentioned, around town is a different story. one thing i did see is i got better mileage in town on my low geared trucks then i did on the highway. they just ran too hard to keep speed.

you got to decide what you want out of your truck. is it gonna be a low end stump puller or a top end wind up toy?? a lot of your b uild seriously depends on what the truck will be mostly used for. i worked the crap out of mine, so i always went for the low end towing power.