Need Info on slant 6 to V8 swap

I Just picked u a 66 Dart GT /6 that i would like to up grade to a v8 , I read ALL chat great info. what would be the best power plant to use 340 ? will my slant 6 trans fit any small block V8 trans plant. This Dart GT was purchased from the orgional owner with 35k miles on it .
Thankd
davidd