First of all guys, sorry for asking a question that is probly already on the site...just couldn't find the info i needed during my searches.
Here is what i have...
I am swapping my 79 F-150 4x4's 400 into a 78 F-100 2wd that had a 460. I have all the original mounts from the 460, but i am not sure what/how to swap the mounts to fit the 78. The tranny's are the same. Thanks again for your patience with my (ignorance).

 

I'm sorry, but i have to ask: What in the world are you doing swapping in a 400 instead of a 460? Usually its the other way around. That being said, I think you would be better off buying some new mounts or finding some in the local junkyard.

 

The 4x2 and 4x4 frame pearches are different.

 

I did the swap a few years ago but went the other way. Mine was a 77 460 2wd into my 78 400 4X4. A few things to check are:

Oil pan sumps, front or rear. I think 2wd and 4X4 are opposite. If so the oil pump and oil pick up are involved.

The 400 and 460 motor mount perches are different but may swap from frame to frame.

Check out your exhaust manifolds. Make sure you will be able to re-plumb.

If I remember correctly the fan shroud needed to be modified. I think the 460 fan is a little lower.

All n all the swap is not to tough.

 

My brother did a 400 to 460 swap a while back and the 460 was out of a car. the oil pan sump was in the front of the oil pan, so that caused some clearance problems. the front of the oil pan had about 2-3 inches of clearance over the front axle. So unless u put a lift on your truck, you might have problems.

 

The 460 that came in the truck has a hole in the block about the size of a softball. The 400, i just rebuilt, with flat top pistons, cam, intake, carb. etc. I am just not sure how the crossmember and all that will come into play. Also, if i need to modify the towers in any way to get the 400 to sit where the 460 was. Thanks again for all the input.

 

You will need to get new towers from somewhere in order to get everything to line up properly. The 460 is wider.

 

Nice job on picking the 400. Check out the 335 series engine forum and you'll find a whole bunch of folks who like your choice.