The Boss 429 was not a four valve engine. The 427 SOHC FE engine was a two valve engine. The only four valve Ford engine during the ‘60’s was the Indy car engine that drove the Offy away.
in 1965 the Chrysler Hemi was not outlawed per se. the teams could have used it in the Plymouth Fury or its Dodge equivalenT. It could not be used in the Belvedere or Coronet because they were considered intermediates like the Fairlane and Chevelle. In addition the winged Mopars were not outlawed in 1971 as the media often says. They were perfectly legal but only with a 303 cubic inch engine. They were made non-competitive not outlawed.