Nothing wrong with a F5 they made a great kit. Cammer should be a pretty good fit with some tweaks seeing how they already have the 4.6 as a option. Kirkhams certainly are top of the line in my book. I would also contact Nick Acton of ACE. He's "Mickmate" on the board here and builds a really sweet 427 car to original specs. Nice thing you can buy things as you go along or all at once. I'm sure he can help you on the cammer fitment from the get go. Saves doing things twice. He's right up in NH.
Acton Custom Enterprises Custom Metal for Cobra's soon as my ducks are in a row I plan to visit someday and hopefully get mine underway. Really nice guy and took the time to answer all my silly questions and prices are very reasonable. Good luck the 427 SOHC is somethimg most of us can only dream about. I had to settle for a tunnelport. LOL.