I am looking at a 1994 F-350 4x4 dually with a siezed 460, with the mpg a 460 gets I would like to know if there is a different engine that can be installed with extensive changes??
David

 

Any motor can be installed "with extensive changes"
I don't think the words "F350 Dually 4x4" and "good mileage" can be used in the same sentence. Might as well either rebuild the 460, or put another 460 in it. You are not going to gain much (if any) fuel mileage with anything smaller, and will notice the lack of power.

Just my $0.035

 

I agree. That combination of truck and engine will never get good mileage. Best bet build a 521 stroker, it will get around the same mileage as the 460 (because it doesn't have to work as hard) but when you need a little extra it will definately be there. Big Cubes=Lotsa Gasa so there's no easy way out!