I had a '79 F-150 that I switched out the 351M for a 400 and everything went in spot for spot, being the same block, and I never regretted it. As long as you keep the oil issues in mind, taking steps to help secure the oil pump to the bottom of the block so that the **** continues to flow, the engine will do you well. My brother tried to contend that his 460 was vasty superior, but I did a load of research and found out that a decently built 400 can put out 90% of the HP and torque a respective 460 can at only 80% of the RPM's, and putting that kinda power into a FSB would be an awesome ride (and an excuse to get to upgrade drivetrain parts ;-) ) I still have my engine (currently sitting in the truck corpse) if anyone in the Wisconsin area is interested in any of the parts. Now that I have my Bronc with me in Alaska, the 1/2 ton has fallen to the wayside. Anyone interested can get in contact with me at
[email protected] and we can make arrangements.