Radiators: Is 22" enough for 400 HP?

Look at SlantSixDan's method of using 2 runs of 10ga wire with 4 fuses, better servicabilty than fusible links.
Check out Crackedback's headlight relay setup also.
I love the fan swap to Ford fans but it is not super cheap and requires some thought. If you have questions there are a couple guys on here that can help walk you through it. I learned what I know from them.

Here are some tips-

If you source the fans from the yard then you get all the connectors and low-speed resistor. You will need these. The brand new Dorman fans wont come with them. The factory fans, even used, may be of better quality.
I mounted the Dakota Digital fan controller above the high beam switch on the footwell, it is a handy spot to wire to and be accessable. The wiring can be hidden by the kick panel.
The relays can be mounted to the bottom of the battery tray out of sight, I have my vacuum pump under there, so mine are mounted in the corner of the inner fender along with the 60A fuse.
A good temp guage such as an Autometer Pro Comp will get you a compatible sender to run with the fan controller.

You should be able to source a 78amp square back alternator fom the parts store, but look at the output ratings carefully, as some 78 list actual output as 60amps.