273 Supercharged...ITS HAPPENING PEOPLE!!
Should run 400 horse easy. I ran a 273 in my 1968 4 door for yrs. Street/strip car. 10.5:1 compression, 557" solid purple cam, rpm intake, 700 holley dp, 1.6 rockers, 904 trans., 4800 stall turbo action converter, 4.88 gears. All added up to 12.60 1/4 mile at 104 mph and 1.60 60 ft. Good luck. I loved the under dog quality of yhe 273.