I'm reconsidering adding forced induction to my planned 440/512 stroker. Say for instance I have an A518 transmission, a 440/512 lightened with aluminum parts, EFI, headers, Voodoo cam with a custom grind, and the properly ported heads. I've heard of similar engines getting 16-18 mpg with just a carburetor and 3.55 or 3.54 gears, with EFI I think I might be able to eek out 20 on the highway. How much power would I gain, and would I lose any fuel mileage, if I decided to build it for lower compression and put on either a turbo, twin turbo, or say, an F2 Procharger? Pros and cons to those different systems? I also thought about compound boost, using some sort of turbo setup and a supercharger. Thoughts?

What 512" engine gets that fuel mileage?
I haven't checked what my 512 EFI engine with 3.54:1 gears and 5-speed OD transmission gets, but I doubt it gets over 15 mpg?
With a supercharger, you can make more power than the stock engine block can handle (over 800+ hp)

512" and fuel economy don't really go together well in general. Especially when you start porting heads and adding cam, that will be going in the wrong direction to maximize fuel economy.

If you're after mega fuel econ. build a turbo small block. You could take a near stock 318/360, get great fuel mileage, and make 500hp+ pretty easily.

My car when it had the 9:1 360 in it with the 2.76 gear and 727 would get around 15mpg on E85 without even attempting to jet for fuel curve. Ran 10.60's at that point on around 13psi of boost.

But what you should really ask yourself is, how much will that fuel economy gain cost you vs. what you'll spend to get it? If you drive 5000 miles a year, and save 2mpg at $2.50 a gallon. You're only talking about a $70 a year difference. Can't buy too many parts for $70 a year.

I get gallons per mile

I think you need to rethink your plans on this motor and forget about fuel mileage Buy a fuel sipper for better mileage and build the car to put a big old grin on your face when you get on it Compound supercharging or and compound turbocharging is done for a reason, to force more air into the cylinders, not for fuel economy or fuel mileage Me thinks your dreaming big dreams, get real for now

My last 440 went through over five gallons of fuel breaking in the cam and five pulls, 20 mpg?

16 to 18 mpg with a carb / 18 to 20 with EFI? Keep dreaming! The best I can get out of my 512 with EFI, a Gear Venders and 3.54 gears is 14.5 if I keep it under 70 MPH on the highway. As soon as I start having fun with it the MPG drops like a rock . Trust me, it takes a lot of fuel to feed a 512.

Just for reference, I run a 496/EFI/5 speed with .81 OD 3.23 rear and 25.x" tires. 243@.050" cam. It gets about 14 MPG @ 75 MPH or a little better. EFI is dialed in with lean mixtures and plenty of ignition advance at light cruise.

I think Mopar Rich (fastman EFI) does a bit better with a stroker and more tuning tricks.

That said, I do not believe 20 MPG is "in the cards" with a BB stroker. I am happy to get 14 MPG. Displacement, parasitic losses and not so great Aero work against fuel mileage.

The reason modern powerplants are turning to boost is to get more specific output, so you can achieve 300hp out of a 2.0L rather than needing a 5.0L NA engine. Boosting does not improve fuel economy, downsizing does.

Compound boosting is often done for improved transient response, now we are starting to look into Electric superchargers. With 512" and some sort of higher stall converter, I don't really feel the extra effort is warranted, unless you just want a project.

Advances in chamber/port design don't hurt either, so if you were to choose a more modern starting point, say a Gen III Hemi, then add boost, you could end up with similar power to your RB stroker (assuming you are running a stock block), with better efficiency.

Good luck!