Brainstorming Session: Building a (relative) gas meiser

[79 silverado]

Start off by saying theres no way short of insane expenditures that we could ever expect to see a 70s C/K truck getting great mileage relative to an econobox. Thats said, how about looking at a repectable output? I'm considering 2 somewhat different platforms, and brainstorming, and would like to see other's opinions on the subject.

I picked this forum as I thought it'd be a nice general interest topic these days, but if the mods disagree (even though its not a solve my problem deal) feel free to shift it into tech....

In their stock forms:

Platform 1: 1977 GMC 4x4 1/2 ton 6' step, 250 I-6, TH350, part time 4x4 (would think its a np205 right?) non-ac truck, d44/12bolt rears

Platform 2: 1980 Chevy 1/2 ton 8' fleet, 350 v8, TH350, 2wd, a/c equipped, 12bolt posi

Again, very different starting points, but I can go with either one at this point, they're both in the garage already

Now, As a starting point lets keep the budget under $1000-1500 to work with for the sake of this experiment.

The final truck WILL have a tire with a profile of about 29" tall: either a 235/75/15 on the 2wd truck or most likely a 215or220/75/16 on the 4x4. Either rim would be aluminum in nature -my excuse to rationalize that one? have to also reduce rotating mass hehehe.

Beyond that, gearing and tranny are somewhat open-ended. I do not know the current gear ratios in either truck offhand, thats something that based on the final formula could be changed. Carbs? Again, open to speculation. Overall horse power is not the goal, just adequate get up and go so the engine isnt working to hard to move a nearly 5000# truck.

Before I start the brainstorm remember I'm talking true mpg after accounting for the fact larger than stock tires will show the odometer reading fewer miles than actually experienced (similar to how the speed reading is normally off)

Initial thoughts that came into my mind for the 1980 were a 4 to 2bbl adapter on the 350 to put a dualjet on there off a 305 (or maybe swap to 2bbl intake), coupled with around a 3.08 gearset, headers with less restricive exhaust and no cat, electric fan to cut the rotating weight on the front of the engine, and maybe even switching out the pulleys if its affordable for a starting package.

On the 77 I was thinking upgrade the ignition, custom mandrel header into a no-cat single 3" pipe exhaust, electric fan (again reduce rotating mass on engine), and somehow switch up the intake/carb as well. To be honest I had contemplated something exotic (although most likely problematic) where I know that some I-4 iron duke s10 guys use an adaptor to mount a carb onto their FI intake, maybe with a upsized injector to compensate for the extra cubes and a fabbed up adaptor a, early 80s s10 TBI unit could be adapted onto the I-6?

Again, the idea here is to have fun. Anyone who's tinkered with things to get better mileage I wanna hear em. I'd like to put together a reliable truck that will get in the mid to hopefully upper 20s while on the highway for a cross country tour at the end of the summer... I can see it now... everyone is gonna think im

That said... BRAINSTORM TIME