i had an old 4mm stock cylinder motor that made 77hp. my brother had a 4mm stock cylinder motor from FAST that made right at 80hp. they were both running ass bikes.
you can achieve everything you want with a stock cylinder 4mm setup. you will still be able to dune or trail ride it and be able to turn on the speed when youre wanting to beat on those pesky 4 stroke riders.
build it right with keihin 33 or 35mm pwk carbs, v force reeds, pod filters, noss head and domes, pipes and timing and you will tear up those 4 strokes.