Brian is right. Only 221 to 351W will fit without mods.
I have a 351C in my 62. It does however require mods to the shock towers. The 351C will drop straight in however there is only approx 1/2 inch clearance between 2 exhaust ports and the shock towers on each side.
There are 4 ways (that I know of) to get around this.
1 - Do a test fit then sledge hammer the shock towers at the offending exhaust ports. This is functional but ugly. You'll also need custom headers. Manifolds won't fit.
2 - Same as 1 however instead of the sledge hammer, weld in curved sections in the shock towers where the exhaust needs to go. This is the method I used. The advantage is unless you really know what you're looking at it looks like it left the factory that way. You will however need custom headers (I built my own). Manifolds won't fit.
3 - Use something like the crites kit. This will give you a bit more room. The crites site does gove some good pics of what's invloved.
4 - Go the whole hog and remove the shock towers. This does require rack and pinion steering along with lots of other mods (sorry I don't have any experience with this). This will give you lots of room to fit anything you like (well maybe not a rolls royce merlin!!)
You'll also need to up the radiator. I don't know of any factory one that will fit and do a good job. In Australia I would recommend Aussie Desert Coolers in Melbourne. They can make you a 3 or 4 core radiator for this application.
I don't have any suggestions on headers as I made my own. You can try contacting the Compact Fairlane Club of Australia. They have lots of expertise with the 62-65 Fairlanes. Sorry I don't have contact details in front of me however there is a link to the club from the RubberConnection web site (
www.rubberconnection.com).
Hope this helps
Tim