What engine could i swap in place of a 460cid to get better gas mileage?

I'm looking to get a 95 Ford F250 that has a big block 460cid that has 400 ft. Lbs. Of torque. Is there an engine i could swap in it's place that gets close to 30mpg and will still have some get up and go?

This is the beauty of that 460. It can pull 18 tons and still get the same mileage. It is a workhorse of a truck. If you don't plan on working it, this is not the truck for you. You can cam it, up the compression, adjust the gearing, add bigger injectors and a custom flash and then since your building way more power, itll theoretically use less fuel with no load on it, but face it, the 460 isn't a honda car.
my grandpa built my crank. He wouldnt let me see what magic he did, but i'm pretty sure he removed a little rotating mass of the counterweights and some rod material, and also opened up and chamfered the oil holes. It took him about 8-9 hrs locked in the shop with me at the door trying to sneak in and see what he was doing. He had it jigged on 2 pillar block bearings and the rods and pistons right there. The scale was out and it was all done the old way, by hand. That 460 could rev way above 6k and the downside it only carried 20-25 psi oil pressure when warm. This engine did not have anything but a stock pump, stock is good enough for almost any engine.
i know of a fella who used a turbo 4 cummins with a custom adapter mated to the big od 5 speed and installed it in a 99-06 super duty with very good results. Ton of work including modding the trans tunnel. End result decent power, and economy. Lot of people are doing this swap. Its not the monster the big diesels are, but do decent. Cummins makes quite a few 4 cyls that are economical. Anyway if i was gonna go that route, id use an l10 cummins, they create ground shaking power without the big truck displacement and economy

Vehicle weight has far more bearing on MPG than the engine size. How to you plan to reduce the weight of the truck enough to get 30MPG? You will never get 30MPG in this vehicle except in your dreams.

Not in a truck

Have the same truck.

To get almost 20mpg more you would need to put a tiny i4 in there, drill about 2500 holes in the frame, remove the body and bed, replace with carbon fiber streamlined body, some pizza slicer wheels, and require a delicate throttle foot.

360 in front of a c6 in this era i think. Still won't get even close to 30 mpg. Might see something close to 25 mpg's w/o a tail gate on level road @ 35-40 mph w/1" oversized wheels/tires driven **gingerly**. Eh, dunno actually. Prolly a pipe dream there. Even so, soon as you put a load in the bed or are aggressive in any way, all figures will tank big time…
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in support, to add,
this is a utility vehicle. Cost effective to use when fully loaded. Only in N.America do we use trucks as daily drivers. To make a utitilty platform get *fair* mpgs, that didn't happen till well after the obd2 era. The advent of VVT and VVT-I (varriable valve timing, w/or w/o inteligence) was the key.
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"Is there an engine i could swap in it's place that gets close to 30mpg and will still have some get up and go?"

not gonna get "get up and go" AND good mpgs. Get up and go requires more fuel. More fuel is counter productive to mpgs. So doesn't work that way. All a metter of compromises.
my suggestion is to buy an mpg platform and use the truck as a *truck*. Strickly a utility platform only. And use it fully loaded. It will then be very cost effective vs work done over time. Which is how one should calculate a *utility* platform's cost effectiveness.

Nope none

You need to sell your truck and buy a diesel, but still 30 mpg is tough. Trade for a new Ram 1500