A 0.60 over 283 is a 292 I built a number of them back in the early 60s they were vary popular street race eng back then we also built a lot of 125 over they 4 in bore and made it a 301 were real popular before chevy made 327 cu in widley avalable yhe 301 ran really hard untill ta got them hot ya had to wait for them to cool down