Verified answer

Yes a 400M can be made to perform was well as stock 429. But the 429 is a far better choice for a performance build.

Yes,

How We Got Over 500hp from Ford's 400M Engine - Hot Rod MagazineCheck out how this Ford 400M engine was able to put out over 500hp with Ford, Chevy, ... fuels left the 400 castrated in terms of its performance potential. ...

http://www.hotrod.com/techarticles/engine/hrdp_070...

351M/400 Performance Build Up

I chose to use a Holley model 80457S on my high-performance 400. .... How to Rebuild Ford Engines V8, Covers 351C/351M/400/429/460. ...

http://www.projectbronco.com/Technical_Articles/35...

Engine Tech Power Secrets of the quot 400 Cleveland quot Revealed ...Odd really, considering it's very "performance oriented" heritage. Background. The 351M / 400 engines came at a time when Ford's Windsor plant couldn't keep ...

http://www.off-road.com/trucks-4x4/project/project...