i dont think its possible. the only way to get 510 ci from an FE is to start with a 427 block with the 4.23 bore, and i think i remember reading that back in the day they used to offset grind the cranks to 4.375 or something which is close to 510 ci. i believe that the 427 block with a scat 4.25 crank gets around 485 ci. With a 390 block and a scat stroker kit you can get anywhere from 410-460 cubes respectively and close to 470 with a 428 block. I fought this for a long time myself trying to figure out how i was gonna punch my 390 out for big cubes and mega hp. I built a healthy 416 using a factory 428 crank. Its a nice motor, and the FE's are cool, but eventually had to succumb to the fact that a 460 is already a 460 and for cheaper than i could build a 450ci FE I could build a 550ci 385 series. So i sold the FE for 460 money. Not sayin you should ditch the FE's, but if your wanting 500+ inches a 390 isnt the best place to start