Mancini or Muscle motors would be the first people I would talk to , Hughes is his own worst enemy , difficult to deal with .
The 512 kit seem to work well , you can use the longer 7.1 " con rods & short pistons without putting the oil ring over the wrist pin , durable & torquey pkg .
With ported iron heads you can make 600+ gross hp & over 700 ft lbs tq with good drivability , all below 6000 rpm ,which is great for typical street use . The heads limit the top power to around 5500 , with better heads you can move the powerband up if you desire