I was running late to work one day, and the top seem on my radiator blew out, while doing 75-80 mph (that's the third time it happened in 6 years. Never did figure out why.) The engine sucked in a good portion of the coolant, and didn't like it! I made it the last three miles on 5-6 cylinders, and it didn't get hot until the last 1/2 mile(those FEs are tough). Anyway I had a 460 with a C6 out of a 83 F250 HD that I got for free. Both had less than 20,000 mi since being rebuilt. I ordered swap mounts that where wrong(for swapping from a small block)then ordered more, and was very unimpressed. for $150 you would think you'd get decent welds. After some trial ,and error I ended up welding bolts to the factory mount plate of the 460, and moving the trans cross member to the forward set of holes. Everything fits like it was made to be there, so if you want solid mounts don't waste your money. I expected vibration but it's not bad at all you would never know it's solid mount.
my questions are. Is the 460 lighter than the 390. Does anyone know the weights. My front end sits 1 1/2" higher, causing a camber issue. I've heard that the I beams can be bent by chaining them to the frame, and using a bottle jack. Has anyone ever done this, and is it recommended. Is a old school radiator up to the task of cooling the 460 until I get something better. Also where can I get a wiring diagram that is correct the colors and overall scheme don't match my Chilton manual. I suspect because the donor truck was a HD. I by on the 68 with a mustang manual. The colors, and circuit are all the same on the early fords.

 

The 460 is heavier than the 390. Your truck may simply have to be driven for the front end to "settle". If not, I would take the truck to someone experienced with cold bending I-beams.
As far as the wiring goes, you should be able to use your old wire harnesses, alternator, etc.