A big inch hemi can make 650 easily...if youve got the bucks & someone who knows hemis, to build it. A friend has a 500 in low deck twin turbonthat makes 1200 hp. ..With ac & 410'sj 5spd, all in his 70 'Cuda. Super street friendly. And there not too many street cads fhat will hang with it. Cruises 65 @ 2500 rpm. Turbo a big inch low deck for almost the price of a well built hemi, with all the good stuff. Im twin turboing my 68, 3100 lb 4spd low deck cuda..