I got a 454 chevy bb and im woundering what should i put carburator or go fuel injection. i want it to hall ass when i step on it but when im cruzing i want it to save gas.    (oh yeah its going in to a chevy single cab short bed truck)  

Well, first thig is, there's no such thing as "saving gas" with a big block.

That aside, depending on what year truck you have, the carb is gonna be easier to setup and simple to operate. The FI will give you a slight power increase and economy gain.

Shooting form the hip, I'd say go with the carb.  

You can save gas with any engine. You just won't save as much with a big block given the extra friction, rotational weight, pumping losses, and maximum lean air/fuel ratio necessary to produce useful work.

A properly-tuned multiport EFI will yield dramatic fuel savings over a carb. Moreover, the EFI can boost low end torque with much longer intake runners than any 4bbl carb.

The simple keys to increased mileage (without cost prohibitive tricks such as electric assist, cylinder deactivation or engine shut-off) are: (1) cutting weight to the minimum, (2) reducing frontal area, (3) reducing drag as much as possible, (4) reducing frictional losses, and (5) turning the engine (regardless of size) as slowly as possible at cruise.  Of course, sizing the cam/intake/head/header package to maximize efficiency at low r.p.m. helps.

Just look at how the OEMs build MPG.  The Dodge Viper runs fuel injection with a 3.08 rear gear and a 0.5 overdrive (1.54:1 effective final drive ratio).

And I've heard about an obsolete, economy-cammed, low compression, iron head Mopar 440 hooked to a non-overdrive 727 Torqueflite that produces about 60% better fuel mileage after being swapped out of a heavy Maxivan and into a lighter and smaller Dodge Raider SUV and paired with a 2.26:1 geared Ford 9" third member.  And there's still a lot of potential mileage on the table . . . .

Weight, aero, drag, friction and engine speed-- these are the variables for maximizing m.p.g.  

I'm gunning for 30mpg with a Buick 455. May or may not make it, current setup (Q-jet, 4-pin HEI) is at 23mpg. New engine is a MegaSquirt Multiport EFI w/ 7-pin HEI.  After the engine is in I'll re-gear the car to suit what the engine likes for cruising (at what point the low end torque is sufficient not to bog the engine at 70mph).  Currently it's 3.23 gears with a .64 Overdrive in a TKO-600 and 1800-1900rpm at 70mph.  

Cool!

Unless the cam is really big, a 455 ought to pull a gear in the mid twos with a TKO-600.   That'd give up some low end grunt, though.

During the last gas crisis, C.J. Baker (then at Hot Rod) used to advocate 2.73 gears (no overdrive or EFI of course), claiming that with his BBC Chevelle combo, he only gave up about 3/10ths in E.T. in exchange for a signficant mileage boost.

I tried this in a GT0-powered Pontiac LeMans and found the E.T. reduction to be about double what C.J. reported.

Also back then, Doug Marion achieved surprising results with "Bonneville" gears in PHR's "Econoperformer" Monte Carlo. However, he used a lot of other strange stuff with his SBC, such as very long tube 4-2-1 headers and a now out-of-production Edelbrock intake (no Overdrive or EFI).

Hopefully, somebody will figure out how to retrofit GM's Displacement-on-Demand hydraulic lifters and oil-control solenoids onto vintage big blocks (with a suitable manual control system) so we can see some real mileage gains.

Until then, I wonder if there are still any Cadillac V8-6-4s at the JY and if those rocker arm deactivator solenoids could be modified to work with roller rockers . . . .  

The EFI typically boosts low end torque over a carb, so I'll see how it goes when it's in, sometime in June or early July and select rear gearing accordingly.