anyone build 400m's

[hotrodlincoln]

i have a 1979 lincoln mark 5, i have a 400m and its got 20k on the rebuild,great engine just a bit lethargic. what do i need for more power and fuel economy? i dont plan on spinning more than 4800rpm and its just a cruiser.any help would be great[

 

[old lady's mad]

i built one once , if you ask me its a truck motor . all kinds of pulling torque . but no real raw power . fuel mpg. your kidding right ? its a work motor . dont try to make it anything else .